Ep 163 Circadian Rhythm: Live from Perth, Australia

Episode Transcript
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Speaker 1 (00:00):
Good morning, Erinds.

Speaker 2 (00:01):
Good morning everyone, and thank you for the invitation to
come and share a story that I went through my career.
In twenty twelve, I was an intern back in Dublin
in a large teaching hospital. I was six months after
finishing my intern year, aged twenty three, and I was
working in a busy surgical unit. It was January and

(00:22):
I was woken up about six am to go and
start my journey to work. As I've gone to work,
I've where in mind.

Speaker 1 (00:31):
It's a Thursday.

Speaker 2 (00:31):
I've already undertaken about thirty six hours of work within
this work week from Monday, and I'm about to go
and start on another Thursday. I feel I'm relatively well rested,
but I know that I'm not feeling particularly good going
in to start a very large shift, which I'm going
to elaborate on a little bit now. At six point thirty,

(00:52):
I arrive into work and I undertake results checking. We
look at all the results of our patients from the
day before, recent blood tests, recent scan results, and ultimately
to prepare for the ward round when our surgeons and
the consultants and the senior doctors will start undertaking looking
at every patient on their list. At seven o'clock, we

(01:13):
start sharp and we finish about eight o'clock. And at
eight o'clock those senior surgeons will head off to surgery,
and us as the junior doctors, will then undertake.

Speaker 1 (01:20):
The tasks of the day.

Speaker 2 (01:22):
We'll look at organizing consultations, We'll be writing letters, discharging patients,
admitting new ones, and then deal with problems as they
occur on the wards. It's fast paced. It's a busy unit,
but it's something.

Speaker 1 (01:36):
That I thrive.

Speaker 2 (01:37):
I enjoy the challenges as they present. I really am
passionate about the work and I'm very happy to work
in such a busy environment. Even though you might only
be getting twenty minutes for a quick lunch break, you
feel very valued, You feel wanted and a key cog
in that machine of the hospital. But there's very much

(01:58):
a drive. You have to have the work done and
it has to be done correctly. It's got to be
done with precision, because at the end of the day,
patient care depends on it. As the day continues, we
tick over to about quarter to six in the evening,
and then the surgeons are starting to come out of
theater and then we start doing a further round through
the hospital again of all the patients that have been

(02:19):
under the lists, of the surgeons whom have operated, and
those who are still waiting after their operations. These rounds
then can finish about quarter past seven. So bear in
minds I've been in the hospital since six point thirty
and it's now quarter past seven at night, and then
start the next part of my shift. And back in
twenty twelve, we were routinely rostered to do twenty four hours,

(02:39):
So I will then move from my day job to
then providing night cover in the tertiary hospital, of which
there are only four interns. All of us have only
done six months prior, and we're all fresh out of college,
maybe twenty three, twenty four to twenty five. We each
cover in the region about one hundred and eighty patients,

(03:00):
each with one senior doctor to call upon for assistance
as we go.

Speaker 1 (03:04):
Through the night.

Speaker 2 (03:05):
Now, usually you would get a scattering of sleep here
or there of a few hours, maybe hold each other's pages.
This particular night in question, that was not going to
be one of those cases. We were dealing with six
patients across the hospital and in my particular area that
I was looking after I know offhand I was dealing
with the patient who was having an acute stroke on

(03:27):
the middle of the ward, as well as a patient
who was bleeding post operatively on the ward and trying
to get them back to theater for emergency surgery. Jobs
kept creeping up as we went through the night, and
they did not stop. But then we were getting to
six point thirty in the morning, and I was then
starting to get set for the next ward round, which my.

Speaker 1 (03:45):
Team were getting prepared for.

Speaker 2 (03:48):
And it's at that point that I've been notified that
we have a sick doctor on and I'm going to
be required to stay, and my boss has asked me
to stay and conduct surgery with them. Now, I'm not
a surgeon, and I'm working under complete supervision of very
senior surgeons at the time. I'm not putting any patient
within risk because I'm simply holding a retractor. I'm not

(04:10):
doing anything that's going to be compromising them. It is
simply to be able to hold something in theater and
provide that extra bit of support so the surgeon and
their assistant can do their work under full supervision. At
that time, I finished and wrapped up about eleven thirty
in the morning and I'm excused, at which point I've
probably been awake for about twenty nine hours and scatterings

(04:33):
of sleep here or there. I make the decision to
drive home, and nobody forced me to make this decision.
I took that completely on myself. And as I'm driving
down the Grand Canal in Dublin, I fall asleep at
the wheel and I wake up with a jolt and
I've put my car into the back of a large
Dublin bus. I get out of the car, look at

(04:56):
the smashed windscreen, completely obliterated bonnet, and smoke coming up
the engine. I'm shaking. I'm uninjured, but really fraught with
anxiety and just fear of what's happened. I call my dad,
who's been a fantastic wealth of wealth of advice and
support for me over the years, who helps me to

(05:18):
navigate the situation in relation to getting insurance, calling retrieval authorities, etc.
To get the cars off the road. He slowly makes
his way to come and see me on the Grand
Canal dock, and as traffic starts to move on, we
get the daggered looks of the frustrated drivers whose days
have been interrupted by my accident. But my dad has

(05:41):
been a wealth of advice over the years, says to
me is that this has been a very valuable learning
curve for you, and you've gone through it without anybody
being injured. And for me, that was what was really interesting,
was because now as I reflect back on that, my
life could have taken a very different turn. Not only
was I uninjured, but I did not injure anybody else.

(06:02):
And it's something that it really does strike fear in
me that I didn't only put myself in a position
of danger, but I put others in danger and it
only cost me the price of my car, not the
cost of someone's life or my own life, and leaving
a family potentially having an injured family member or even
my own family where they would have to have dealt

(06:23):
with my debt because of the decision I made. But
in reality, I was far too fatigued to make that
decision correctly. And as I said, no one forced me
to do this. This was something that I did on
my own bat and it's something I reflect on every
day as I go to work, whether I'm making sure
that I am not in a position where I can
make an error like.

Speaker 3 (06:42):
That again, that is just a terrifying and very relatable story.

Speaker 1 (07:32):
And I'm glad that you were okay.

Speaker 3 (07:34):
I'm glad everything turned out okay, and just thank you
very much for sharing the story with us.

Speaker 4 (07:39):
Yeah, thank you. We're so glad, like you said that
the accident wasn't worse than it was, and we really
appreciate you sharing it with everybody here today. I think
it's something that unfortunately a lot of us can probably
relate to. So thank you so much, thank.

Speaker 5 (07:51):
You for having me. Thank you. Hi.

Speaker 4 (07:58):
I'm Aaron Welsh and I'm a'm an update and.

Speaker 3 (08:01):
This is this podcast will kill You and we are
coming to you live with our very first recorded live
episode from Perth, Australia, The Lovely Perth. We're here at
the twenty twenty four AIOH Annual Scientific Conference and Exhibition
and we are just thrilled to be here.

Speaker 1 (08:19):
We really are.

Speaker 4 (08:19):
Thank you all so much for having us. A huge
thank you to Zach and Kelly and David and everybody
who helped organize this conference. We are truly honored to
be up here today speaking with you all.

Speaker 3 (08:30):
Really and in light of the fact that we are
at the annual meeting of the Australian Institute of Occupational Hygienists,
and we just flew across one million time zones to
get here, not an exaggeration. We decided to focus on
a topic that is of central importance to pretty much
every industry, and that is fatigue, specifically fatigue caused by

(08:52):
disruption in our circadian rhythms in the context of shift work.

Speaker 4 (08:56):
And because that alone is such a huge topic that
there's no way that we could fit it all into
a ninety minute plenary, We're not going to make you
sit here for one hundred hours. Don't worry, We're going
to take you through just a few parts of that.
So first I'm going to focus on what do we
mean by fatigue, how do we define that, and what
does that actually mean, how our circadian rhythms actually work,

(09:19):
and how disruption in circadian rhythms can lead to symptoms
like fatigue, excessive daytime sleepiness, and so many other chronic
health conditions.

Speaker 3 (09:27):
And then I'll get into how our understanding of circadian
rhythms has evolved over time, the changes that led to
shift work becoming as widespread as it is today, and
how we came to recognize those negative effects of shift work.
And then we're going to bring on a subject matter expert,
doctor Ian Dunkin, who will share some of the current

(09:47):
exciting research that's going on on circadian rhythms and how
to combat the negative effects of things like shift work
and jet lag.

Speaker 4 (09:55):
Yes, but first, no episode of our podcast this pla
I Guess We'll kill you would be complete without a
beverage that we call a quarantinie or in our case
of place berta, because we don't have any alcoholic spirits
in it.

Speaker 1 (10:09):
But we are drinking one today. Today we're drinking TikTok.
You don't stop get it because it's like a clock. Yes,
it'll be funny. We explain jokes so that they're not
funny anymore. But in TikTok, you don't stop.

Speaker 4 (10:27):
There.

Speaker 3 (10:27):
It's a delicious beverage consisting of one ingredient, which is
Australian ginger beer.

Speaker 1 (10:33):
So thank you.

Speaker 3 (10:33):
It's delicious and also easily modified. You can add whatever
spirit you would like or just leave.

Speaker 1 (10:39):
It with a little bit of lime in there. Delicious.

Speaker 4 (10:42):
Sorry, we should have really had the foresight to make
a drink for everyone, like under your seats you can
find oh, my gosh, very Oprah.

Speaker 1 (10:49):
Cheers to you all.

Speaker 4 (10:53):
Okay, now, drinks are drunk, shall we We'll get into
the biology of are circadian with us?

Speaker 1 (11:01):
I can't wait. Yeah, tell me all about it.

Speaker 4 (11:02):
It's going to be fun. So we decided to do
this talk today on fatigue because it's kind of this
universal experience that also happens to be an occupational hazard

(11:25):
in so many different industries.

Speaker 1 (11:27):
Everyone has at.

Speaker 4 (11:28):
Some point been fatigued experienced fatigue. But when we talk
about this idea, what do we actually mean, Like, how
do we define fatigue?

Speaker 5 (11:37):
Right?

Speaker 1 (11:38):
It's super easy to define, right, Right, there's not a definition.

Speaker 4 (11:42):
There is not a single definition of fatigue, but there
are a lot of different definitions. Most of them use
a lot of synonyms, things like tiredness or exhaustion. Most
of the definitions include something like the decreased ability to
function at your normal capacity or something of decreased capacity
for mental or physical work.

Speaker 1 (12:03):
Okay, So overall we're.

Speaker 4 (12:04):
Looking at fatigue as this generalized lack of energy that
overall has some kind of impairment on your ability to function,
be that your physical function or your cognitive function.

Speaker 1 (12:15):
All right, makes sense?

Speaker 4 (12:16):
Okay, And following but in that definition, what's important about
it is that we then have to intentionally separate fatigue
from sleepiness.

Speaker 1 (12:23):
Right, right, And how does one do that?

Speaker 4 (12:25):
How does one do that by defining sleepiness?

Speaker 1 (12:29):
Okay, more definitions, more definitions.

Speaker 4 (12:31):
So we can do this by defining sleepiness as directly
related to the physiologic phenomenon that is the act of
falling asleep, okay, because that means that it's something that
we can measure, okay, at least to a better degree
than we can fatigue, which is so nebulous. Right, And
we do this. We can measure sleepiness with a couple
of different tests. There's one called the multiple sleep latency test,

(12:54):
which is I'm going to put you in a dark
room and you're going to lay down and fall asleep.
How long does it take you?

Speaker 1 (12:59):
Wow? Not stressful at all, right.

Speaker 4 (13:02):
And then there's also the maintenance of wakefulness test, which
is how long can you stay awake if we sit
to you in a dark room and ask you to
not sleep.

Speaker 1 (13:11):
We have to be sitting just sitting with your thoughts
in a dark room. No, I don't like that idea.

Speaker 4 (13:17):
Now, sleepiness itself like falling asleep, It's not a bad thing.

Speaker 1 (13:21):
Inherently, we have to sleep.

Speaker 4 (13:23):
It is required of all humans, and as humans are
diurnal species, we have evolved to sleep.

Speaker 1 (13:28):
At night when it is dark and be awake when
it is light.

Speaker 4 (13:32):
So being sleepy at night time itself is not a
bad thing, but if that sleepiness is happening when we
shouldn't be asleep, then it can lead to what's called
excessive daytime sleepiness, or this inability to stay awake during
hours when you should be awake, and that can be
bad or, as we heard in our first hand account,
even downright dangerous. Both excessive sleepiness and fatigue, though they

(13:57):
are different, and these definitions are important, also kind of
two halves of a story, and they both contribute to
the kinds of accidents and workplace events like we heard
about in our first hand account. And while circadian rhythm
disruptions themselves are by no means the only things that
can cause excessive daytime sleepiness or fatigue, these are two

(14:18):
of the most immediate consequences that we see from circadian dysfunction.
So having a basic understanding of what our circadian rhythms
are and how they work can go a really long
way to understanding what happens if they get pushed out
of sync, which then can lead us to better anticipate
the hazards that might be inherent to some professions, or

(14:40):
recognize these symptoms when they start to crop up during
certain phases of life. Hello newborns, Gotta love them. And
then evaluating and understanding these consequences of this type of
circadian disruption can help us to actually implement strategies in
the future to help mitigate some of these.

Speaker 1 (14:58):
Hopefully we'll get there. Yeah, can it be done?

Speaker 5 (15:00):
Can it? So?

Speaker 4 (15:02):
Then, first we have to start with what really is
circadian rhythm? And I think most people probably have a
sense of what this.

Speaker 1 (15:08):
Means in their mind right.

Speaker 4 (15:10):
It comes from the Latin circa means about and ds
or DM means.

Speaker 1 (15:14):
Day stole my line, Yeah, thank you, I try so.

Speaker 4 (15:19):
When we talk about a circadian rhythm, we're talking about
cycles that are happening in our bodies on an about
twenty four hour timeframe. And Aaron, I know later you're
going to talk about why we have these rhythms. Yeah,
like from an evolutionary perspective, yep, what are they.

Speaker 1 (15:34):
Doing for us? It's they're important? Are they? Let's find
out yeah.

Speaker 4 (15:38):
But I'm going to focus first on how they actually work.
And everyone is probably most familiar with a circadian rhythm
in the context of sleep and our sleep wake cycle,
because our sleep wake cycle is one of the most
classic examples of our circadian rhythm in action. So we
can see a few different things that oscillate in our

(15:58):
sleep wake cycles. One of them is something like melotone
in secretion. So our melotonin peaks in the couple of
hours before we go to sleep, and then we'll go
to sleep, our corticol levels will peak in the morning
right about the time that we tend to wake up.
We also see oscillations in our body temperature, with the
lowest body temperature happening in the wee hours of the

(16:20):
night while you're still asleep.

Speaker 1 (16:22):
I just want to ask why for each one of these.

Speaker 4 (16:25):
I don't have great answers, but I can tell you
that what these like the why is that these processes
together are what are driving our drive for wakefulness okay,
and our pressure for sleep okay. So these three things,
they're not the only things that are involved in what's
literally keeping us awake during the day and telling our
bodies we need to go to sleep at night.

Speaker 1 (16:46):
But these are three of the big.

Speaker 4 (16:48):
Drivers of that drive for wakefulness that happens during the
day and that pressure for sleep that happens through like.

Speaker 1 (16:54):
Towards the night. But what's the deal with temperature?

Speaker 5 (16:57):
Oh?

Speaker 1 (16:57):
I don't know? And also what is.

Speaker 3 (16:58):
That so use the body? But are changes by how
many degrees?

Speaker 4 (17:02):
I knew you were going to ask that, and I
meant to like look it up again to try and
get in. I don't know.

Speaker 3 (17:08):
I don't know that it's twenty it's just the fool Yes,
like a proportions of a degree.

Speaker 1 (17:14):
Yeah, yeah, yeah, Okay, we're little changes.

Speaker 4 (17:16):
But it's enough that it's sort of in that period
when we're close to waking up. That drop in temperature
is what helps our bodies stay asleep essentially, right, it's colder,
stay asleep, et cetera.

Speaker 3 (17:27):
Rkay, Okay, explain why didn't sleep well when I have
that power?

Speaker 4 (17:32):
Yeah, we're going off track. So, as humans, because we're diurnal,
we see these particular cycles again on this twenty four
hour clock where sleep is happening at dark and a
week time is happening during the light. So this is
what we all think of when we think of circadian rhythm.
But it is not just this our circadian rhythm, like

(17:52):
literally every single function and process in our bodies from
the cellular level, like the genes that are controlling which
cells are going to divide, when the genes that are
controlling DNA repair, does it happen in what cells? And
when things like our immune system, our metabolism, our hunger cues,
our bowel movements, our libidos, every function in our body

(18:16):
is controlled to one degree or another by circadian processes.

Speaker 1 (18:20):
It's like the ultimate but weight. There's more. It's not
just sleepwake, it's everything.

Speaker 4 (18:25):
Everything, and these all are our circadian rhythms. It's not
just sleep, but sleep is a big part of our
circadian rhythm. And these circadian rhythms are mechoganized internally in
our bodies by what's called an intrinsic circadian clock. But
not just one clock. We have multiple clocks. We have

(18:46):
a main clock in the part of our brain that's
called the super chismatic nucleus.

Speaker 3 (18:51):
I'm really glad that you pronounced this because I just
wrote SCN over and over again.

Speaker 1 (18:56):
I don't even know if I talk about SCN. But no,
now I.

Speaker 4 (18:59):
Know how to pronounce the SCN or the super chismatic nucleus,
and this region in our brain functions as like a
master regulator of our internal clock. But all of our
peripheral cells and tissues, they all have clocks of their own,
and together all these clocks drive our many many circadian rhythms,
in large part by the build up and then the

(19:19):
breakdown of specific proteins whose literal job it is to
be made build up and then break down on a
twenty four hour cycle to keep these clocks all in
sync with each other.

Speaker 1 (19:34):
Okay, does that make sense?

Speaker 4 (19:35):
Yeah, it's like pretty basic, right, super simple.

Speaker 1 (19:39):
I'm sure it took no time at all to figure
that out.

Speaker 4 (19:41):
No, no, no, So that's how these circadian clocks are working
on like a cellular level. And I said that these
are intrinsic, and we know that these are intrinsic because
these cycles will persist on an.

Speaker 1 (19:54):
About twenty four hour basis.

Speaker 4 (19:56):
In humans, it's a little long. We tend to run
about twenty four hours and ten minutes.

Speaker 1 (20:02):
I got eleven in here.

Speaker 4 (20:03):
Eleven minutes, eleven minutes, nine to eleven is what the
literature says.

Speaker 3 (20:08):
We can have a rate anywhere from nine to eleven
minutes and twenty four hours.

Speaker 4 (20:12):
And twenty four hours and eleven minutes nine to eleven
and our clocks keep doing this even if we put
someone in a dark room with absolutely no external environmental
clue cues like in absence of the environment, our clocks
still run. However, these environmental cues are in fact an
essential part of our circadian rhythm because a lot like clocks,

(20:35):
old tiny clocks, not new fangled watches which work by magic.

Speaker 1 (20:39):
Is how my magic I watch works.

Speaker 4 (20:41):
Okay, old tiny clocks mechanical ones you used to have
to wind in order for them to keep correct time.
Our circadian clocks also have to be wound in order
to keep them on as close to a twenty four
hour cycle as possible, and this happens through a process
called entrainment. And the environmental cues that we use for

(21:03):
entrainment in our circadian clocks are called zight gabers. Which
is my attempt at German, and that is German for timegiver.

Speaker 1 (21:12):
How'd she do?

Speaker 4 (21:13):
Did anyone speak German?

Speaker 1 (21:14):
And not?

Speaker 5 (21:15):
Great?

Speaker 4 (21:15):
I can tell I tried really hard.

Speaker 1 (21:20):
Zight gabers.

Speaker 4 (21:21):
In humans, it is light, predominantly light from the sun
that acts as our number one zyp giver or time giver,
and the sun light from the sun is detected by
these specialized cells in the back of our eyeballs that
project directly to that SCN, the super chismatic nucleus, and
that part of our brain again is this pacemaker that

(21:44):
coordinates the cycles in all of the rest of our body.
And they do this, they coordinate the timing of like
so many different processes, right through direct and indirect pathways
to keep us on this twenty four hour cycle in
sync with the sun or the light around us. Now,

(22:05):
light is by no means our only zight gaper. Food
can be a powerful one, especially for other mammals other
than humans.

Speaker 1 (22:12):
We also can.

Speaker 4 (22:12):
See, exercise, social activity, other things can serve as zitkeepers,
but light is by far the primary one that our
particular clocks use, which means that although these rhythms are
generated internally, they do require entrainment, mostly via light in
order for so many of our biological processes to match

(22:34):
our environment. So when our environment changes, like when we
travel across exactly nine time zones I counted between California
and Western Australia to come to a conference ten for me,
suffice to say, our internal clock no longer matches our
external environment.

Speaker 6 (22:51):
I'm feeling okay, though I will say thank you caffeine.

Speaker 4 (22:54):
Yeah, that's a big part of it, right, And we
all know this particular phenomenon very well. This is jetlag.
And with jet lag, because of this discrepancy between your
external environment, the timing of light exposure, and where your
internal circadian clock was set before you left, you end
up feeling pretty terrible. Right, not myself, not today right now,

(23:17):
we feel great, but you can end up feeling pretty terrible.
You might have symptoms like a really hard time falling
asleep when it's time to fall asleep, or maybe you
simply cannot keep your eyes open for like an afternoon
meeting when you get to where you're going. And because again,
this malagested timing is affecting every body system that we have,

(23:38):
not just sleep, it's not just being fatigued or being
excessively sleepy, you might also have gi upset, mood changes,
brain fog, and so much more. Now, in addition to
regular old jet lag, there's also a phenomenon called social
jet lag.

Speaker 1 (23:57):
We'll separate it all.

Speaker 4 (23:58):
Right, and social jetla is basically this idea that we
all as like a society at large, not us in
this room here. We have all decided that our day
starts at like eight am, right, or whatever we can
say for it, and that is where the day is
supposed to start for everyone across the board.

Speaker 1 (24:17):
But a lot of us.

Speaker 4 (24:18):
Maybe end up relying on like our alarm clocks to
wake us up on the weekdays to be able to
get ready for work on time.

Speaker 3 (24:24):
A lot of us, I mean of us who doesn't
that would be amazing?

Speaker 4 (24:29):
Yeah, And then when that happens, many of us might
perhaps on weekends, when our schedule permits it, sleep in later,
go to bed later, stay up later. So we have
this shift in what our schedule looks like between weekdays
and weekends. And it turns out that different people might
feel differently. Some of you might be like, oh, yeah,

(24:49):
I do that, and others are like, noth dude, six am, I'm.

Speaker 1 (24:52):
Ready to go.

Speaker 4 (24:53):
That's because we all have different chronotypes, and a chronotype
is like different natural tendencies to either sleep early or
sleep late, like early bird, night owl. It's a real thing.
Which are I'm an early bird.

Speaker 1 (25:04):
You're an early bird? Like so what is the threshold? Like?
What a fun question? I don't know. I don't know.

Speaker 4 (25:11):
I don't know if there's like a specific thing.

Speaker 1 (25:13):
And can you be neither or can you be like
a light early?

Speaker 4 (25:16):
You can be neither, you can be whatever you want
to be.

Speaker 1 (25:18):
Okay, are you an early bird? I think about mild
early bird.

Speaker 4 (25:22):
Mild early bird?

Speaker 1 (25:23):
Ye like and not too early? Yeah bird?

Speaker 3 (25:25):
Yeah, I don't want the first word.

Speaker 1 (25:28):
One would be fuels.

Speaker 3 (25:29):
Are still left at the book and want them all gone.

Speaker 4 (25:34):
I love that I'm an early very early No, No,
probably not.

Speaker 1 (25:39):
Maybe I wish I was. It's too much.

Speaker 4 (25:42):
But for people, especially who veer more night owl, then
they might have an especially hard time waking up for
that eight am start every day.

Speaker 5 (25:51):
Right.

Speaker 4 (25:51):
This is especially true for teenagers. And that's not just
a stereotype teenagers. Actually we see shifts in their intrinsic
circadian clocks during the teen years, and like.

Speaker 3 (25:59):
Most teenagers at least in the US, start their days
at like.

Speaker 1 (26:03):
Before seven, right, which is do we do it? It
was miserable.

Speaker 4 (26:06):
It wasn't my idea. And so this system of forcing
these early wakings on some days and then maybe seeing
a shift in what your patterns are like on the weekends,
it can end up causing chronic sleep deprivation. And so
that's what we see in this phenomenon of social jet lag,
and that's something that a lot of us have probably
experienced to one degree or another. But we also then

(26:27):
have even more severe or persistent disruptions in our circadian
cycle that can result from a more chronic forced mismatch
between our environmental cues and our intrinsic clocks. And this
is what we can see in shift work. So across
the globe, it's estimated that anywhere between ten and thirty
percent of all adults in industrialized countries.

Speaker 1 (26:49):
Which is a lot.

Speaker 4 (26:50):
That's a lot, work in shift work. And often if
you work in shift work, then you might end up
working outside of a traditional eight to five of like
a regular old job, and that might mean you're working
night shifts. And night shifts, of course, are going to
require a complete flip of your circadian.

Speaker 1 (27:06):
Cycle where you have to adapt to working.

Speaker 4 (27:08):
Entirely during the dark hours and being asleep during the
light hours.

Speaker 1 (27:13):
Right, But it might not just be night shift. It
can also mean rotating shifts.

Speaker 4 (27:18):
It can mean late afternoon shifts that bleed into night time,
or it can mean early early morning shifts that require
you to start your day before the dawn.

Speaker 3 (27:27):
My mom was an afternoon night shift work, or an
afternoon worker as a nurse. But she loved it because
she would just lay out at the pool until three pm.
She said, she was like, I loved it, and then
I would go home. And maybe she is she a
night owl, not anymore.

Speaker 1 (27:43):
Because that would track.

Speaker 4 (27:46):
But so all of any of these scenarios can serve
to end up disrupting our circadian clock because they're disrupting
the typical timing of our light dark exposure. In a
lot of cases, it might be exposing our eyes and
thus our brains to light essentially twenty four hours a day.
And while sometimes people can adjust the timing of when

(28:08):
they're asleep and when they're awake, like maybe they sleep
just fine during the day, they like sleeping in late
and then laying out in the sun or whatever, what
we do see is that the vast majority of shift
workers do not show a complete shift in all of
their circadian rhythms, meaning things like their melatonin secretion, as
an example, will still happen at night time, and in

(28:31):
some cases can be up to twelve hours out of
phase from when they're actually sleeping. Wow right.

Speaker 5 (28:37):
Yeah.

Speaker 4 (28:37):
There was one paper I read that estimated that only
about twenty five percent of people who work night shift
long term actually show evidence of having a lot of
these circadian rhythms actually being shifted in line with their
real life. Wow right, it's a pretty low percentage, okay.

Speaker 3 (28:54):
And this is like continuous night shift work, not like
rotating shift work or like two weeks on two week
two exactly.

Speaker 4 (28:59):
This was a people who are like night shift for
the long term. Yeah yeah, And so this can unsurprisingly
result in what's called shift work disorder, which is a
disorder that can be characterized by things like insomnia, which
is difficulty falling asleep or staying asleep, or it might
be excessive sleepiness like falling asleep when you shouldn't be
at work or micronapping. But it can also lead to

(29:21):
increased irritability, it can lead to mood changes like depression
or anxiety, and it overall can lead to this mental
fog that can lead to increases in mistakes because of
all of this fatigue and sleepiness. So some studies suggest
that working during the night alone increases the risk of
workplace accidents by forty to one hundred percent.

Speaker 1 (29:42):
WHOA, which is huge.

Speaker 4 (29:43):
It's a huge range also, but it's also huge, like
very significant. And shift work disorder alone is not that uncommon.
Some papers estimate up to twenty seven percent of shift
workers meet the formal definition of shift work shift work disorder.

Speaker 1 (30:00):
But on a practical.

Speaker 4 (30:01):
Level, everyone who has work shift work has probably experienced,
to one degree or another, this negative effects of this
circadian disruption. Yeah, but again, it's not just fatigue and
sleepiness at work or outside of work, because especially what
we see with time spent working night shifts having really
significant impacts on long term health. Shift workers are at

(30:23):
about a twenty to thirty five percent increased risk of
breast cancer, prostate cancer, colorectal cancers, but also type two diabetes,
coronary artery disease, and depression and many other chronic health
conditions as well.

Speaker 3 (30:38):
Eric, But like, what is the mechanism for that? Like why, Yeah,
what do we know about that?

Speaker 4 (30:43):
We don't know everything, which is a classic line, and
I will say that there has in the literature been
some pushback as to like how causal is this relationship
because a lot of these disorders also have a lot
of other lifestyle factors that influence them as well, and
so sometimes you might see difference in lifestyle between people

(31:04):
who work shift work or night shift work specifically compared
to day shift workers and things like that. But the evidence,
especially for cancers in animal studies, is so significant that
circadian rhythm destruction in animal studies leads to cancer formation,
tumor growth. And it is such overwhelming evidence that the

(31:25):
International Agency for Research on Cancer named night shift work
a probable carcinogen all the way back in.

Speaker 1 (31:32):
Two thousand and seven. Wow, this is like a new information.

Speaker 4 (31:35):
But then if we dig even deeper on like what
is the mechanisms, we know that our circadian rhythms are
affecting so much of our overall body functions, and what
we see is that disynchrony of our sleep wake cycles
and our endogenous circadian rhythms ends up leading to things
like increases in blood pressure, reduced insulin sensitivity, elevated lipid concentration,

(32:00):
and so all of these might put us at risk
for things like diabetes, hypertension.

Speaker 1 (32:04):
Cardiovascular disease.

Speaker 4 (32:05):
There's also some evidence between like timing of and amount
of melatonin secretion and the effects on uncogenesis or cancer formation.

Speaker 1 (32:14):
That's interesting exactly.

Speaker 4 (32:16):
So at like a basic level, what it's thought to
be is that all of these increases in risk are
a result of the fact that so many of us
working night shifts. Our endogenous circadian rhythms do not adapt
to this forced pattern of being a weak.

Speaker 1 (32:31):
At night and being asleep during the day.

Speaker 4 (32:33):
So it's a mismatch between our internal cycles and the environment.

Speaker 1 (32:37):
So that's the best answer I've got. I mean, I
think that's a pretty good awer.

Speaker 4 (32:41):
Parts it is, yeah, and probably a lot of specific
mechanisms that go into each of the different disorders and
things like that, But on the whole, I think I've
convinced you all that it's abundantly clear that our circadian
rhythms are very, very integral, not just in our sleeping
and our weakness and our alertness or fatigue, but also
in so much of our health. So circadian rhythms are

(33:04):
an important thing to consider in the context of a
lot of our stages of life, a lot of our professions.

Speaker 1 (33:10):
So I have a question for you erin uh huh,
ask go ahead.

Speaker 4 (33:14):
If this thing, these things, these circadian rhythms that seem
today to be it's so easy for us to disrupt them,
to get get messed up. You just hop on a plane,
just change.

Speaker 1 (33:24):
Your clocks back, just go into a grocery store at night.

Speaker 5 (33:27):
Right.

Speaker 4 (33:28):
If it's so easy for them to get disrupted, and
when they get disrupted, they can cause so much trouble,
why do we have them? What do they do for
us as humans or creatures like you?

Speaker 1 (33:40):
And when?

Speaker 4 (33:41):
How did we know all of this? Tell me everything?

Speaker 3 (33:43):
Okay, I'll tell you as much as I can tell you,
maybe not everything. Wherever you are, whether you're here in

(34:07):
this room in Perth, Australia at this conference, or you're
tuning in from across the world. I want you to
imagine yourself as a dot on the globe, as a
pin on the map I've.

Speaker 1 (34:18):
Marked Perth here.

Speaker 3 (34:21):
Now, let's rewind time, let's say two hundred million years
or so, keeping that pin in its original coordinates, and
I want you to picture a time lapse of the
continents shifting, colliding, separating, oceans, expanding and shrinking, mountains forming
and crumbling.

Speaker 1 (34:41):
What is your pin witnessing in all of this?

Speaker 3 (34:44):
Has it mostly been a drift in a vast ocean,
or has it been at the center of continental action,
witness to collisions and separations, or maybe your pin has
seen it all. As our time lapse comes to an
end eventually and the continents have settled into the familiar positions,

(35:05):
let's take a minute to marvel at the incredible dynamic
changes that our planet has seen over those two hundred
million years, which is just a fraction of the Earth's
four and a half billion year existence. Grasslands turned to deserts,
rainforests turned to freshwater lakes, and temperature rainfall and atmospheric
composition shifting tremendously over these millennia. Life on Earth has

(35:30):
had to deal with a lot of change, even just
over those two hundred million years. But throughout those transformations,
there has remained one near constant. The sun always rises
and the sun always sets.

Speaker 1 (35:45):
I love that so profound.

Speaker 3 (35:48):
And while the time between sunrise and sunset varies across
latitudes and seasons, the existence of a day has always
been a feature of life on Earth. So let's go
back to your pain the map the two hundred million
years ago, the day you'd experience outside of like having
to fight and hide from dinosaurs, is nearly identical to

(36:09):
the one that you'll experience today, just about an hour
shorter thanks to the Earth's s gradual slow down. In
a world filled with so much uncertainty, it can be
reassuring to have that one constant. And this sentiment is
shared across much of life on Earth. Most organisms have
evolved to anticipate these daily changes. Plants, animals, fungi, algae,

(36:34):
even cyanobacteria all possess internal clocks that control the timing
of biological, physiological, and behavioral responses.

Speaker 4 (36:42):
We love that we see it, even in bacteria, likely fascinating.

Speaker 1 (36:47):
It's so cool. I also love that someone looked for that.

Speaker 4 (36:49):
Right They're like, we've got to find it here.

Speaker 3 (36:52):
It's not just us, It's not just us, it's everyone.
Or is it? Is it that I don't know.

Speaker 1 (37:02):
Rhetorical question.

Speaker 3 (37:03):
But these behavioral responses, or these biological responses, things like sleep,
like the release of certain hormones, or like feeding that
occurs at certain times of day or night, and we
call these rhythms that are these responses that repeat over
a roughly twenty four hour period, of course, are circadian rhythms.
The ubiquity of these rhythms across all or almost all

(37:26):
of life. I guess I don't know what's going on
in like the worms that live in the deep sea events.

Speaker 1 (37:31):
Whether they have they always mess things up.

Speaker 6 (37:33):
I don't know, they could have. They probably still be
something we'll find out. Yeah, well we'll look into it.
But it just speaks to how important these rhythms are.
But why why would it.

Speaker 3 (37:45):
Be so crucial to partition our activity or our physiology
across a twenty four.

Speaker 4 (37:50):
Hour period, That's my question?

Speaker 1 (37:51):
Why does it matter?

Speaker 3 (37:53):
In a word, optimization, Our external environment changes in many
ways every day, availability, predator activity, temperature, When other members
of your species are also out and about, you want
to spend your energy where it counts. If you're a
bird who relies on color vision for foraging for berries,

(38:15):
you probably want to do that during the day, when
the light actually helps you pick out those colorful berries.

Speaker 4 (38:21):
See them, you can actually see helps.

Speaker 3 (38:24):
But if you're a small prey mammal species like this
flying squirrel, maybe running around at night is your best
bet to escape predators or flying around.

Speaker 1 (38:33):
You also don't want to be active all the time.
It will be exhausting.

Speaker 3 (38:37):
Our sleep is incredibly important for housekeeping tasks that our
body can't do while we're running around, and circadian rhythms
help us optimize how we spend our energy and when
it's safe to get the rest that we need to recuperate.

Speaker 1 (38:52):
Anyone who has pulled an.

Speaker 3 (38:53):
All nighter or who has had to run on a
few stolen hours of sleep after welcoming a newborn knows
the pain of being out of sync with the world.

Speaker 1 (39:02):
But for the most part, we can easily.

Speaker 3 (39:04):
Recover from these one time or short term disruptions. But
what happens when there is a constant mismatch between your
internal clock and the external environment.

Speaker 1 (39:13):
Well, we know from what you.

Speaker 3 (39:14):
Just told us, Aaron, that it's really not great, not
good for humans at the least, not good for most,
if not all, of the animals we've studied, and decades
of research have shown that it's not great for really anything.
So let's take a minute to get into the story
of how we came to understand these rhythms of our
lives and the consequences of their disruption. Humans have recognized

(39:36):
circadian rhythms in ourselves and other creatures for millennia. Aristotle
in the fourth century BCE noted that bees slept bees,
bees slept fourth century BCE.

Speaker 4 (39:50):
I love that they're just cutting open hives, being like, oh,
that one's asleep.

Speaker 1 (39:53):
Oh yeah, I'm sure. Sorry, you're disturbing up like this.
Very's so cute.

Speaker 3 (40:00):
And around the same time and Rosthenes observed the leaves
of the tamarin tree curling and uncurling over a day.
The famous ancient Greek and Roman physicians Hippocrates and Galen
described fevers that peaked at certain times of day.

Speaker 1 (40:14):
What do we think that might be?

Speaker 4 (40:15):
I love this, it's malaria, it's larious, probably, yeah.

Speaker 3 (40:19):
And one of the leading hypotheses for why these cyclic
fevers exist is that the parasites match the circadian rhythm
of their host or their mosquito vector for more likely transmission.
Like is, do they go into the bloodstream at certain
times a day so that that's when the mosquitoes are biting.

Speaker 4 (40:34):
It's really that's not malaria.

Speaker 1 (40:38):
It's horrible.

Speaker 4 (40:38):
Yeah, but they and the parasites are like going to
be active at certain times to maximize transmission.

Speaker 1 (40:46):
That's I know, mind blowing evolution. Man, it's pretty cool.

Speaker 3 (40:51):
But for centuries, all of these observations remained just that observations.
No one attempted to answer the question of why until
them seventeen twenties, when a French scientist by the name
of de Meran decided to take a closer look at
a plant, specifically Mimosa pudica, which also goes by the

(41:11):
adorable common name of sensitive plants or.

Speaker 1 (41:14):
Shy plant or shype so I used to call it.

Speaker 3 (41:17):
And anyone who is interacted with this plant can see
where it got its nickname. When you touch its delicate leaves,
they fold in on themselves like ah, don't touch me,
and then a few minutes later they'll open back up,
though they calm back down. But it turns out that
the plants also do this folding and unfolding routine throughout
the day, folding up at night.

Speaker 2 (41:37):
Day.

Speaker 3 (41:37):
Moron, observing this, thought to himself, what if the two
words at the heart of every scientist, what if they
aren't exposed to light?

Speaker 1 (41:46):
Then what happens?

Speaker 3 (41:48):
And so he plopped the plant into a dark cupboard
and saw that it still opened and closed its leaves
over that twenty four hour period.

Speaker 1 (41:55):
Wow, even in complete darkness.

Speaker 3 (41:57):
And so if light wasn't driving this pattern, what was
In eighteen thirty two, about one hundred years after day
Morn's experiments, Swiss botanist Augusta. Kendall took this question further,
placing MOMSA plants under continuous light. Initially, the plants still
show their daily leaf movements, but as the days went on,

(42:19):
the candle watched as this pattern grew out of sync
with day and night. Something internal, like an internal clock,
perhaps it seemed to be driving these movements, governed by
a cycle slightly shorter than a day, around twenty two
hours compared to twenty four to Kandle's experiment was the
first to demonstrate the concept of a free running rhythm,

(42:42):
where an organism's internal clock is slightly longer or shorter
than a full twenty four hour day, and in the
absence of external cues, their rhythms will eventually decouple from
that twenty four hour cycle and instead be guided by
their internal ones humans, for instance, twenty.

Speaker 1 (42:57):
Four and twenty four hours then nine to eleven minutes.

Speaker 3 (43:02):
But, as it often goes Dick, Kendal's conclusion that organisms
are guided by an internal clock as opposed to responding
solely due to external stimuli was not immediately embraced.

Speaker 1 (43:13):
Shock imagine that.

Speaker 4 (43:14):
We learned something new and not everyone believes.

Speaker 3 (43:17):
The debate on whether these daily patterns were directed by
internal or external forces continued basically up to the middle
of the twentieth century, coinciding with the peak of the
nature versus nurture debate, But while nature versus nurture seemed
to be only increasing in contentiousness, research on rats, plants, birds, bees,

(43:39):
even humans demonstrated clear evidence for an internal clock cut
off from external cues. Mice and rats kept running on
their wheel or sleeping right on schedule.

Speaker 1 (43:50):
Chickens who had been incubated at.

Speaker 3 (43:52):
Constant conditions still hatched with an innate biological rhythm. Bees
demonstrated a keen sense of time and an ability to
communicate that time.

Speaker 1 (44:02):
These are just an amazing example.

Speaker 4 (44:05):
Rhythms and flower time in really good I have to.

Speaker 3 (44:08):
Like schedule, like have a little schedule calendar for oh,
ta this flower then, because that's when it's producing nectar.

Speaker 5 (44:14):
Right.

Speaker 4 (44:14):
They have it all in a little notebook.

Speaker 1 (44:15):
I just imagine getting there a little early and they're like, oh.

Speaker 3 (44:18):
My gosh, you'll wait, wait, this is where's the nectar?

Speaker 1 (44:21):
Yeah, got places to be. Next one opens in five.

Speaker 3 (44:29):
And humans turned out to be no exception to this,
as a series of cave, Arctic and.

Speaker 1 (44:33):
Underground bunker experiments demonstrated.

Speaker 3 (44:36):
The first of these took place in nineteen thirty eight
when physiologist Nathaniel Kleitman called his graduate student Bruce Richardson
into his office one.

Speaker 1 (44:45):
Day this is how I imagining how it went, and.

Speaker 3 (44:47):
Said, hey, Bruce, can I interest you in an all
expenses paid, thirty two day trip to Mammoth Cave, Kentucky
where we'll hang out in a cavern and try to
adjust our bodies to a twenty eight hour day. The
nearby hotel will take care of our gourmet meals. You
can bring whatever books you'd like.

Speaker 1 (45:03):
I've got a deck of cards to play bridge. It'll
be great.

Speaker 4 (45:06):
One deck of cards, thirty two days.

Speaker 1 (45:08):
Yeah cool, Well that's all you need really really, but bridge,
just bridge.

Speaker 4 (45:12):
I don't even know how to play bridge me either.

Speaker 1 (45:14):
Two conditions though.

Speaker 3 (45:16):
You've got to record your sleep movements and your temperature
at regular intervals.

Speaker 1 (45:21):
Richardson said, yes, I mean, who wouldn't like I would
do this? That sounds fun.

Speaker 4 (45:26):
I tried his advisor and he's like, well, I can't
say no.

Speaker 1 (45:29):
That's true.

Speaker 5 (45:29):
Yeah.

Speaker 1 (45:30):
I tried to do it with ticks. Do you remember this.

Speaker 3 (45:32):
I was sampling in Panama and I tried to measure
see if there was like a diurnal pattern of tick abundance.
And then the rainy seasons a three am. Yeah, and
I got rained out and I had.

Speaker 4 (45:43):
To leave and this is over.

Speaker 5 (45:44):
Yeah.

Speaker 1 (45:45):
It was exhausting new experiment. Yeah, I never I never
did it again though. Oh well, opportunities for the future.
But while the scientific.

Speaker 3 (45:54):
Conclusions drawn from this end of two experiment just Kleiittman and.

Speaker 1 (45:57):
Richardson, they were a little vague, right.

Speaker 3 (46:00):
Richardson apparently readjusted to twenty eight hours, but Kleitmann did not.
It made quite an impact on the budding field of chronobiology,
drawing the attention of journalists who sketched a story of
scientific adventure, as well as researchers who wanted to try
it for themselves, like Michel Sifrey, who spent two months
in a cave in the Italian Alps in nineteen sixty two,

(46:22):
waking and sleeping when he felt like it. Ultimately, when
he emerged, he was shocked to find that he had
lost two weeks. He thought I'll just it'll be exactly
where I think.

Speaker 1 (46:33):
But no, no, he lost two weeks because he's too long.

Speaker 3 (46:36):
And this work helped to incite interest into the study
of circadian rhythms, and by the early nineteen sixties the
field of chronobiology was born, with one of its leaders,
Franz Hallberg, introducing the term circadian rhythm in nineteen fifty nine.

Speaker 1 (46:51):
Seems so recent, I know it is. I mean internal clock.
I think was at least from the eighteen hundred. This
this is the term rhythm more recent, Okay.

Speaker 3 (47:00):
Since then, researcher has examined the process of entreatment which
you described, and I was thinking about zeit Gabers Again,
apologies for the pronunciation as kind of like right now,
how you're giving a talk and you think, oh, I'm
right on time, I'm doing great, and then someone at
the back holds up like a five minute warning and
you're like, whoops, I'm only halfway through my presentation.

Speaker 1 (47:20):
I feel like that sign is a psyche Gaberah. It's
a good analogy. I like it.

Speaker 3 (47:24):
Researchers have examined the mechanistic basis of how these external
signals are received by the hypothalamist eyes, pineal gland, or
by some other means. They've attempted to decipher the genetic
basis of biological clocks, identifying clock genes and observing how
these genes synchronize across our body to orchestrate broad physiological

(47:45):
and behavioral changes during a.

Speaker 1 (47:47):
Twenty four hour period.

Speaker 3 (47:48):
They've done a lot, Yeah, a lot, and this research
has been integral to understanding what drives the rhythms of
our life, why they're important, and what happened when they're disrupted,
which brings me toune dune.

Speaker 1 (48:03):
Dune shift work.

Speaker 3 (48:05):
Shift work has been around forever, or at least for
thousands of years, standing guard, keeping the fire lit, watching
over your flock of sheep, caring for the sick or wounded.
The military and certain trades have long required irregular hours,
like shipbuilders who had to work with the tides, or
rope makers. I found a quote by a rope maker

(48:26):
from seventeen forty two. We cannot make ropes when the
sun shines. We begin at eight o'clock at night and
work till eight in the morning, and sometimes we work
all day if we can hold it. I don't know
why I tried to look into it. And I even
asked like blue Sky, and I got varied answers and
some fun hypotheses. But if anyone knows or is an

(48:47):
idea they have to work at night, please reach out,
come find me. But until the late eighteen hundreds, shift
work was a fairly uncommon occurrence. Then let there be light,
specifically electrical life. In eighteen ninety two, just three years
after the invention of the light bulb, the first power
plant in New York opened, supplying continuous powder to those

(49:10):
who could receive it. The effect on industry was immediate.
Factories that had to shutter their doors shortly after the sunset,
or who used lanterns or gas lights for overnight work,
could now operate around the clock, bathe in the glow
of artificial light. For the heads of industry, the benefits
of around the clock operation were clear again, the word

(49:33):
optimization comes to mind. Factories could be more efficient while
maximizing production, and a twenty four hour workday broken down
into shifts became the new norm for many industries, even
those that had not previously required continuous labor. Shiftwork was
not just something to give them a leg up, but
it was becoming necessary to survive the competition. It was

(49:55):
apparent that industry was enjoying an economic boom from this
increased productivity.

Speaker 1 (49:59):
But how were workers faring in this brave, new, well
lit world? Doing great? I'm sure doing wonderful.

Speaker 3 (50:09):
Interest in this question grew in earnest over the first
couple decades of the twentieth century, and a new concept
term industrial fatigue was introduced to describe the exhaustion caused
by over exertion to long working hours and insufficient rest,
often measured by a decline in productivity.

Speaker 1 (50:28):
About productivity, Aran, yeah, I mean so.

Speaker 3 (50:31):
Under this framework, human health was reimagined as or equated
to the body's capacity for productivity. So, in other words,
if you're sick, that means diminished output. If you're exhausted,
that means more mistakes, which means diminished output. And this
concern with worker health and productivity, especially when it came
to industrial fatigue, led to the formation of committees such

(50:53):
as the Health of Munition Workers Committee in Great Britain,
who sought to get a sense of the scope of
the problem. One thing became clear people working on night
shift were especially prone to industrial fatigue. So I'm going
to read you a quote from a nineteen eighteen report
by the Health of Munition Workers Committee about night shift.

(51:14):
The objections to night shift may be shortly summarized as follows.
Number one, it is uneconomical, owing to the higher cost
of wages, lighting and heating.

Speaker 1 (51:24):
Number two.

Speaker 3 (51:25):
Supervision at night is not always so good as by day,
owing to less effective lighting or to the employment of
fewer or less experienced foremen.

Speaker 1 (51:34):
Number three.

Speaker 3 (51:34):
The inferiority of lighting may make work, and especially fine work,
more difficult. Number four. The workers may be unable to
obtain adequate sleep by day. This may be the result
of the dislocation of the ordinary habits of life, or
of social causes e g. Noises and disturbances, or the
care of children. Workers are tempted to curtail their period

(51:55):
of sleep through rising to join the family midday meal,
or to some recreation and enjoyment.

Speaker 1 (52:02):
Number five.

Speaker 3 (52:03):
Social intercourse, recreation and amusement may be seriously interfered with,
and number six. Finally, it is not natural to turn
the night into day and to deprive the body of
the beneficial effects of sunlight.

Speaker 1 (52:17):
Not natural, not natural, not natural, not wrong.

Speaker 3 (52:21):
So as far back as nineteen eighteen people recognize the
harm that night shift work could cause, But the next
line in this report reveals the stark reality facing this
kind of work.

Speaker 1 (52:33):
Under existing conditions.

Speaker 3 (52:35):
Night work at any rate for men and women is inevitable.
And those existing conditions that are referenced in that happened
to be World War One, and then they happened to
be World War Two, and then night shift work and
shift work in general stopped being discussed as something that
was an exception to the rule and slowly became the rule,
a normal part of many industries, from transportation to hospitality.

Speaker 1 (53:00):
To entertainment.

Speaker 3 (53:01):
Round the clock work became a fact of life. Many
countries introduced pieces of legislature that limited the harsh working conditions,
especially like long and irregular hours that had become so
widespread during the late eighteenth and early nineteen hundreds, but
shift work remained a staple of industry, growing in prevalence,
particularly through the mid twentieth century. I can share a

(53:23):
couple of old stats here if you please.

Speaker 4 (53:25):
Kind of stats.

Speaker 3 (53:26):
Okay, So these are from a nineteen eighty one symposium
in France. Between nineteen fifty seven and nineteen seventy four,
the percent of shift work across the workforce more than doubled,
from ten point three percent.

Speaker 1 (53:37):
To twenty two percent.

Speaker 3 (53:39):
Wow, and in some industries that percentage shot up to
fifty percent.

Speaker 1 (53:42):
Are over.

Speaker 3 (53:44):
In Great Britain, full time night work was estimated to
increase by one percent every year from the end of
World War II to the late nineteen seventies, which one
percent doesn't sound like much.

Speaker 1 (53:54):
But I have Yeah.

Speaker 3 (53:57):
The bottom line is that over the course of the
twentieth century, we've got more people than we ever have
doing shift work. And accompanying this growth in shift work
was heightened interest in its health effects on shift workers,
as opposed to solely the effects that it had on accidents, injuries,
or lost productivity. Partly driving this change in research interest

(54:19):
was the growing field of chronobiology. While researchers were uncovering
the physiological basis of the internal clocks that guide circadian rhythms,
they were also exploring what could happen if or when
those rhythms were disrupted purpose intentionally and as you might expect,
this research held great interest to both industry as well

(54:41):
as the military. Can a person ever truly adjust and
switch from diurnal to nocturnal spoilers, not so much, not
so much much? And if so, how long does that
switch take and how easy is it to reverse it
go back to normal?

Speaker 1 (54:59):
Can you switch? Is it every two weeks? Is it
every three weeks? Is it a month? Can it be done?
Can it be done?

Speaker 3 (55:06):
How do shift work alter physiology of different systems in
the short term, and what are some potential implications for
the long term.

Speaker 1 (55:13):
By the nineteen eighties and the.

Speaker 3 (55:15):
Nineteen nineties, some of these long term health effects of
shift work were coming into focus. Digestion issues, which had
long been recognized to be a part of shift work,
cardiovascular disease, cancer immune system issues, diabetes, mood disorders, and
a host of social and lifestyle risk factors emerged as
possible consequences of shift work, or, more generally, a disrupted

(55:36):
circadian rhythm and poor sleep. We have made great strides
in our ability to evaluate the links between shift work,
circadian rhythm, and health from epidemiological, physiological, genetic, psychological, and
sociological perspectives.

Speaker 1 (55:52):
All the perspectives.

Speaker 3 (55:53):
We've also come a long way towards understanding how we
can control those risks in the workplace. But as everyone
in this room, everyone listening can attest we've still got
some ways to go to put what we've learned into
practice for sustained improvement and prevention. We've recognized the negative
effects of shift work for over one hundred years since

(56:15):
it became a feature of our everyday lives, and there
are some brilliant minds working on innovative solutions to address
and reduce the impact of circadian rhythm disruptions at both
individual and systemic levels, and we are so excited to
have with us here today one of those brilliant minds,
Doctor Ian Dunican. Like doctor Eilef the provider of our

(56:38):
first hand account, Doctor Ian Duncan is also originally from
Ireland but moved to Perth where he completed his many degrees,
including his PhD in Sleep and Performance, which he earned
at the University of Western Australia. Doctor Dunicin is the
director and Chief Advisor of Melia's Consulting, a scientific consultancy
undertaking research consulting and education, and he also hosts an

(57:00):
produces the Sleep for Performance podcast fellow podcaster. On top
of all of that, Doctor Duncan is also an adjunct
Senior Research Fellow at the University of Western Australia and
is involved in numerous research projects related to sport, shift work, nutrition, safety,
death and psychology. So please join me in welcoming doctor Duncan.
Thanks so much for coming.

Speaker 4 (57:26):
We made this meme just for you.

Speaker 5 (57:28):
Yeah, so just first time I ever heard my name.
I'm brilliant. Together, so we can retract afterwards, INDI da
do where.

Speaker 1 (57:35):
We can cut.

Speaker 4 (57:37):
Thank you so much. We're really really excited to chat
with you. We're going to just pepper you with questions ready. So,
like Aaron kind of has described already, we've known for
a really long time that work that disrupts circadian rhythms
can be pretty detrimental to human health. So if we
look first from a system's perspective, what measures can organizations
or companies take to help reduce the impact of shift work.

Speaker 5 (58:00):
Yeah, it's a good question. I think it's really important
to take a systematic view. Many companies to just chase
one thing and go ooh, let's get technology, let's look
at rosters. So we always advocate a system view, and
we have this paper that we published a couple of
years ago in Safety and Health at Work, which has
fourteen elements and it's very holistic. Some of those key

(58:20):
elements of obviously include things like shifts and rosters, sleep disorders,
which many people really don't focus on. I know you
spoke about sleep happening earlier on. There's over seventy seven
zero recognize disorders by the American Academy of Sleep Medicine
that we follow here in Australia. But typically many companies
just administer a questionnaire like the Airport Sleeping Scale, and

(58:42):
I think that's an actual sleep disorder program when it's not,
So we need to look more holistically there. Other components
include educating our workforce and that's not just a few
slides and induction, that's actually spending two to three hours,
you know, like what you've done here today in more
detail about how to manage shift work at a personal
level around sleep path and diet, nutrition, commuting to work
if travels involved as well. So these are just some

(59:04):
of the elements that we would take in a system
view as well. But another crucial aspect not to be
overlooked is actually staffing, because if we don't have enough
people to do the job, we're just going to lead
to more and over time, more stress on the individuals
and more rework, and so it's very important at the
first level that we have the staff incorrect before we
start trying to implement the system. And finally, on this point,

(59:26):
you don't actually have to have a system that stands alone.
That system could be integrated in your health, your safety,
or other sort of systems there in a business, So
it doesn't have to be a standalone or a newly
constructed system. It may exist in other ones as well.

Speaker 4 (59:39):
Okay, that makes sense.

Speaker 3 (59:40):
Yeah, yeah, And so maybe you're lucky enough to work
at one of these places that does incorporate a more
holistic view of sleep and shift work.

Speaker 1 (59:48):
Or maybe you're not.

Speaker 3 (59:49):
But what can anyone do at an individual level to
kind of reduce the negative impacts of shift work?

Speaker 5 (59:56):
Yeah? I think at the individual level, I think you've
done a really good job, say, highlighting some of the
negative impacts. But what a lot of studies haven't done
is look that what is the benefit of some of
the interventions or case controlled studies where people are doing
something going forward. The first thing I would say to
anybody undertaking shift work is keeping your own physical fitness
and mental health and check is number one. So you know,

(01:00:19):
excessive alcohol consumption that we see excessive nicotine caffeins that
we see in shift workers, we need to bring that
back into normal tolerable levels. When we start increasing our
body weight, that's going to lead to things like sleep
with their breeding disorders, it's going to lead to more
like generalized fatigue that you define that will start as well.
So it's really important that your own physical fitness and
mental health and well being is in checking and shape.

(01:00:40):
And that's really key, I would say for individuals and
also as well when you are away undertaking shift work,
whether it's here in Western Australia elsewhere, like in the
classic fly and flyout, is having a routine. And that
routine doesn't mean going to the pub every night and
having things. That routine may involves some exercise, connecting with
other people, family and friends back home as well. So

(01:01:00):
it needs to be holistic in nature as well.

Speaker 4 (01:01:03):
For the individual just being healthy.

Speaker 5 (01:01:05):
You mean, yes, which is difficult over twelve thirteen hour days,
but you go to mag time. And I would say to
people as well, don't think about going to the gym
as a one or two hour exercise. Even fifteen to
twenty minutes of high intensity exercise can be really good
for you and.

Speaker 3 (01:01:18):
Just having that routine right there were just such a
hard part to maintained.

Speaker 5 (01:01:21):
But it's recially.

Speaker 4 (01:01:22):
Important if you're on those rotating shifts or things like that.
But that makes a lot of sense. Yeah, So a
hot topic, hot button.

Speaker 1 (01:01:28):
Topic these days.

Speaker 4 (01:01:29):
Why we made you this meme is our screens, especially
our personal devices, and especially the use of those at night.
So I want to ask you what do we actually
know about how much these devices are disrupting our sleep
or disrupting our circadian rhythms and contributing to things like fatigue,
and how much of it is the light or the
things that we're doing with our devices.

Speaker 5 (01:01:51):
So do you want the scientific answer or do you
want to clickbdswer.

Speaker 4 (01:01:55):
I don't any more answers that I want.

Speaker 5 (01:01:57):
Because I don't give you a klick answer. It's really
interesting because we did discuss this a few weeks ago. However,
over the last few days there has been a bill
introduced in Australia to band social media. Why yes, so
this was past their day. I believe I'm not getting
into politics and good that's as far as I'll going.
So if we look at electronic device use and its
impact on sleep. There's two ways of looking at this.

(01:02:18):
One is the subjective evidence, how do people report their
feel with electrinic devices? And two is the objective evidence.
What's happening in laboratories with polysymnography, what's happening with actigraphy
of risk warned devices. The subjective stuff is saying, Ooh,
this is really impacted my sleep. The objective stuff is
saying it's not. So. The science and the data and
the quantitative method actually is showing very little of how

(01:02:41):
it's out there. We're currently undertaking a systematic review in
a meta analysis a few scientists around that from around
the world. Russell Foster, who you may know who actually
discovered the SCN he's on that paper with us as well.
And so what we're finding so far self reported stuff,
very influenced I think by the media and the general population.
I've ran two studies and athletes no impact onto sleep. However,

(01:03:04):
there's three mechanisms how they're trying devices may be impact
on sleep. One is the light emitting from these devices
that could be TV, iPad, social media, could be anything
or gaming. Two, the nature or the stimulate and activity.
And many of us in this room do this we
get home, put the kids to bed, do or exercise
whatever it might be, and then we go, oh, a
bit of me time. I put on Netflix, open up

(01:03:25):
my laptop, do some me melts. I check Instagram as
well while I'm having a glass wine and healthy dark chocolate.
And it's always like stimulation plus alcohol plus caffeine, and
then you wonder why you can't sleep.

Speaker 1 (01:03:38):
A single explanation there, and as.

Speaker 5 (01:03:39):
You've explained in your in your reviewerer on is in
the in the graph is when court sool is high,
melatonin can't be released. So we're doing all the stimulate
and activity, we cannot release melatonin or it delays the
time of melatonin. And but also what artificial light may
have that impact, as we said, and the final thing
is that we're replacing sleep time with other times. See

(01:04:00):
example is I'll just watch one more and tonight Yellowstone
as that as well. But the bad part about Yellowstone
at the moment, which is also good, is there's not
one more episode because it comes out weekly.

Speaker 1 (01:04:10):
That's the trick. That's why streaming services.

Speaker 4 (01:04:13):
Yeah, so that's what we can actually blame is Netflix.

Speaker 5 (01:04:16):
Yeah, no, we can't blame Netflix. Yeah, it's on stand
here in Australia anyway. So that's why I'm wearing my
Ora William's boots and belt today. And for Yellowstone I
was going to my wife said no, I recently bought
my scuba So it's it's those three mechanisms, delight the
type of activity and then replacing sleep time. But so

(01:04:38):
far we are not seeing at the finite of link.
A couple of weeks ago we had the Australasian Sleep
Association conference in the Gold Coast and even a massive
study looking at body motion cameras with kids, no results,
no impact on sleep.

Speaker 4 (01:04:49):
Wow, it's so interesting because all of the like recommendations
are still like no screen time one hour two hours
before bed, even like all the sleep you know, organizations
still like recommend that blanket statement, which is so interesting but.

Speaker 5 (01:05:02):
It's not definitive. But I would say the people is,
if you're having troubled sleeping, shift work disorder, sleep on set,
insomnia and trouble winding down, eliminate that activity before bed. Yeah,
lessen that light and just basically use that time to
basically just wind down and candown, which probably leads into
the recommendations on light yep, yeah, exact this is something

(01:05:22):
that we're really saying.

Speaker 4 (01:05:23):
Now, Yeah, that makes a lot of sense.

Speaker 1 (01:05:25):
That makes a lot of sense.

Speaker 3 (01:05:26):
And so this may or may not be a question
of personal interest, seeing as we just traveled across nine
and ten times a.

Speaker 1 (01:05:34):
Million time zones. That is what it feels like sometimes.

Speaker 3 (01:05:36):
But what can we do to minimize or escape the
effects of jet lag?

Speaker 1 (01:05:41):
Like, are there any are there any tips or tricks?

Speaker 3 (01:05:44):
Or are we all just doomed to be sleep deprived
and brain fog and groggy when we cross more than
a couple of time zones?

Speaker 5 (01:05:51):
Yeah? You you really are. But you can't lessen to that.
You can you can? Yeah, the answer is yes, you're
going to be. You're going to be impacted by jet lag.
There's no escape now, there is no biohack. Regardless of
who you listen to on a podcast. You cannot buy
a hackle a jet like. And then people go who
happened years ago? And people came to Australia, they came
on a slow moving shit it's UK six weeks so
slowly or justice. But now we have this rapid transmittitian

(01:06:12):
travel which leads to jet like. So you can do
some preadaptation like with shift work, but a lot of
people can't do that because they're trying to work before
they go. And then you've got to really kind of
use rapid adaption when you get there, and going east
and west will have different effects like switching from days
to nights or nights to days and shift work, and
so there's many things you can do. The number one
thing I would say is light. Light is key. So

(01:06:34):
for you two here today trying to get over jet
like this is the worst environment you come be in.
Nice and dark. Nice include artificial light, no Zeitgerber's no
time givers. It's a bit like a casino, and that's
what they do when a casino, they use all those
things against you to keep you in there.

Speaker 4 (01:06:50):
What's going on?

Speaker 5 (01:06:51):
And now at twelveth midnight that we are now, we've
got no idea what time it is, and so that's
that's what's happening there as well. But with that, I
would say people trying to overcome jet light is light
and natural light as key. So today I would recommend
as much natural light as possible. That's the number one
mechanism you can do. So you need to get and
go straight because you sign get some fresh air and

(01:07:13):
get some movement.

Speaker 4 (01:07:14):
Oh, I love it. We have one last question for you.
It seems like a very exciting time to be working
in these fields in coronibiology and sleep science. What are
you most excited about or most hopeful for in the
future of this field of research.

Speaker 5 (01:07:28):
I think some of the most interesting research is coming
out of Flinders University and Adelette at the moment, and
it's looking at light. Now. I'm separating the word light
from social media and I'm looking at the impact of
light on our health. Like you spoke about artificial light,
people working a nighttime and so on, Sean Ken, Andrew Phillips,
Angus Burns, some of those guys there are doing some
really interesting work around the long term impact of light,

(01:07:50):
and you're using the UK Biobank data to show the
impact on cardiovascular disease, mortality, all of these things as well.
And as you said earlier on, in this in this
research space, still lots to do. But we know that
so far at less than three percent of people can
fully adapt to permanent night shift. And that's very very
few people, but most people think they can. So you

(01:08:13):
cannot buy or hack your way out of this. There
is no free ride and you've really displayed that today.
So what I would say is that the sort of
the light and this science is really key going forward.
And the final part is I think using individual sleep
tracking metrics is really key for the future because we
have to individualize this, and we're starting to look at
individualizing light as well, because people have different sensitivities to

(01:08:35):
like some people can be in a brightly lit room
go straight to sleep, other people can. So looking at
more an individual level of sleep and weight patterns and
individual light sensitivity as well as the next phase I
think we're going to get into that's fascinating.

Speaker 3 (01:08:48):
I now have a million more questions. Yeah, but I
know that we do have to wrap this up.

Speaker 1 (01:08:52):
So thank you so much for sharing your expertise with
us today. That was super fun.

Speaker 4 (01:08:57):
Yeah, we were really excited if everyone here also got
really stoked about this and wants to learn a lot
more about circadian rhythms about shift work. We have a
very long list of the sources that we used to
put together this episode.

Speaker 1 (01:09:09):
There's another page. There's a lot just come and find us.

Speaker 3 (01:09:12):
So yeah, and I've got a ton of sources for this,
but we always shout out just a couple that we
want to specifically highlight, so two in particular. One is
a book by Russell Foster and Leon Kreutzman titled Circadian Rhythms,
a very short introduction published in twenty seventeen, and on
the history of shift work side of things, there was
a great nineteen eighty six paper by Gordon at All

(01:09:34):
titled the Prevalence and Health Impact of Shift Work from
the American Journal of Public Health.

Speaker 4 (01:09:39):
And then I also had a number of sources a
couple really great overview papers about circadian rhythm that I loved.
One was from the Lancet twenty twenty two by Meyer
had All titled Circadian Rhythms and Disorders of the Timing
of Sleep, and that was part of a four part
series that was also really really great. And then another
one from the New England Journal of Medicine by Eleda
and Bass in twenty twenty one, Circadian Rhythms in Medicine.

(01:10:01):
But we had a lot. We always post them on
our website, This podcast will Kill You dot com. Under
the episodes tab, you'll be able to find this list
of all of our sources.

Speaker 1 (01:10:09):
I was going to say, please and your session.

Speaker 5 (01:10:11):
Yeah, yeah, I just released a book today for pre
order on and it's called Thank You very Much. It's
a ghostwriter and it's called a Guide for Sleep, Health
and Shipwork.

Speaker 1 (01:10:23):
I love it and it's got over two.

Speaker 5 (01:10:25):
Hundred and forty references in it and as designed for
people doing shift work organizing sleep and shift work patterns.
It's available for pre order, it's up on LinkedIn, It's
on our website Mellia's Consulting. Fantastic over there and do it.
And tomorrow we have a Fatigue Management symposium from Holt
Past one to Holt Past two and we'll be delving
more into this with five session, five speakers in that session.

Speaker 4 (01:10:45):
Excellent, that's going to be great.

Speaker 3 (01:10:47):
Thank you well, and a big thank you again to
doctor Ilf and also you doctor Dunikan for sharing experience
and expertise with us.

Speaker 1 (01:10:54):
We really appreciate it.

Speaker 4 (01:10:55):
Yeah, and thank you again to Zach Bentley, Kelly Piper's,
David Lowry and everybody body else here at AI Oh.
I can't say it, I know, and I say the
H wrong.

Speaker 1 (01:11:05):
I know.

Speaker 4 (01:11:07):
No, Thank you everyone for inviting us and for organizing
this conference.

Speaker 1 (01:11:12):
We're really really excited to be.

Speaker 3 (01:11:14):
Here and we've got a couple more of our usual
outro episode thank yous, which is thank you to Bloodmobile
for providing the music for this episode and all of
our episodes.

Speaker 1 (01:11:23):
Thank you to Leona.

Speaker 3 (01:11:24):
Sculacchi and Tom Bryfocal for their amazing audio mixing. Thank
you to everyone at Exactly Right, and a huge thank
you to our amazing listeners, including everyone here today. Thank you,
thank you, thank you, and until next time, wash your hands,
you filthy animals.

Speaker 1 (01:11:39):
I've never send that to people in real life. Sorry.

Speaker 6 (01:12:02):
Oh um um

Speaker 4 (01:12:13):
Uh

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.css-14f5ked{margin:0;word-break:break-word;display:-webkit-box;-webkit-box-orient:vertical;box-orient:vertical;-webkit-line-clamp:2;overflow:hidden;}Ep 163 Circadian Rhythm: Live from Perth, Australia