What do chickenpox and shingles have to do with your brain? This week, we dig into two 2025 headline-grabbing studies that link the shingles shot to lower dementia rates. We start in Wales, where a birthday cutoff turned into the perfect natural experiment, and end in the U.S. with a multi-million-person megastudy. Featuring bias-variance Goldilockses, Fozzy-the-Bear regression discontinuities, a Barbie-versus-Oppenheimer showdown for propensity scores – and the hottest rebrand of inverse-probability weighting you’ll ever hear.
Statistical topics
- Absolute vs. relative risk
- Bias–variance tradeoff
- Causal inference
- Censoring
- Confounding
- Fuzzy regression discontinuity design
- Healthy-user bias
- Inverse probability of treatment weighting (IPTW)
- Longitudinal study
- Natural experiment
- Negative controls
- Optimal bandwidth
- Propensity scores
- Selection bias
- Subgroup analysis
- Triangular kernel weights
Methodological morals
- “Propensity scores are the lipstick you put on observational pigs.”
- “Natural experiments are a hot flirtation date with causality.”
References
- Eyting M, Xie M, Michalik F, Heß S, Chung S, Geldsetzer P. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature. 2025 May;641(8062):438-446. doi: 10.1038/s41586-025-08800-x. Epub 2025 Apr 2. PMID: 40175543; PMCID: PMC12058522.
- Polisky V, Littmann M, Triastcyn A, et al. Varicella-zoster virus reactivation and the risk of dementia. Nat Med. Published online October 6, 2025. doi:10.1038/s41591-025-03972-5
- Sainani KL. Propensity scores: uses and limitations. PM&R 2012; 4:693-97.
Kristin and Regina’s online courses:
Demystifying Data: A Modern Approach to Statistical Understanding
Clinical Trials: Design, Strategy, and Analysis
Medical Statistics Certificate Program
Epidemiology and Clinical Research Graduate Certificate Program
Programs that we teach in:
Epidemiology and Clinical Research Graduate Certificate Program
Find us on:
Kristin - LinkedIn & Twitter/X
Regina - LinkedIn & ReginaNuzzo.com
- (00:00) - Intro and first gratuitous mention of sex
- (03:56) - What are shingles, chickenpox, and the vaccines against them?
- (12:30) - Fun facts about the varicella zoster and herpes viruses
- (18:00) - A natural experiment in Wales
- (21:54) - What is the Goldilocks optimal bandwidth?
- (26:17) - Fuzzy regression discontinuity design demystified
- (32:43) - Shingles vaccine vs dementia showdown
- (34:13) - Absolute risk reduction paradox
- (37:44) - Effects for men and women differ
- (41:07) - A giant longitudinal study
- (47:51) - Propensity scores demystified via Barbie and Oppenheimer
- (53:55) - Using propensity scores to make matches
- (58:08) - Inverse probability of treatment weighting demystified via more Barbenheimer
- (01:02:27) - Attempts to rename IPTW for TikTok
- (01:05:59) - Longitudinal study results
- (01:10:00) - Smooch ratings and methodological morals: pigs and hot dates
Popular Podcasts
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.
Las Culturistas with Matt Rogers and Bowen Yang
Ding dong! Join your culture consultants, Matt Rogers and Bowen Yang, on an unforgettable journey into the beating heart of CULTURE. Alongside sizzling special guests, they GET INTO the hottest pop-culture moments of the day and the formative cultural experiences that turned them into Culturistas. Produced by the Big Money Players Network and iHeartRadio.
Crime Junkie
Does hearing about a true crime case always leave you scouring the internet for the truth behind the story? Dive into your next mystery with Crime Junkie. Every Monday, join your host Ashley Flowers as she unravels all the details of infamous and underreported true crime cases with her best friend Brit Prawat. From cold cases to missing persons and heroes in our community who seek justice, Crime Junkie is your destination for theories and stories you won’t hear anywhere else. Whether you're a seasoned true crime enthusiast or new to the genre, you'll find yourself on the edge of your seat awaiting a new episode every Monday. If you can never get enough true crime... Congratulations, you’ve found your people. Follow to join a community of Crime Junkies! Crime Junkie is presented by audiochuck Media Company.