(NEWSER) – It's no news flash that consuming caffeine close to bedtime can interfere with sleep. But scientists at the University of Colorado at Boulder report in the journal Science Translational Medicine that caffeine has another physiological impact on sleep by delaying the body's natural surge in the production of the sleep hormone melatonin, which in turn pushes back the body's circadian clock.

"To our surprise, no one had really tested this question," one of the researchers tells NPR. "What we're seeing here now is another way that caffeine impacts our physiology that we didn't know about before in humans."

Read the full story on