The Science of Study

Caffeine messes up your circadian rhythm, study suggests

It may not be an uncommon thing to drink a cup of coffee just after the dinner or right before the sleep. And some people may or may not experience the changes in their sleep after that late coffee. Well, the recent study suggests that caffeine, coffee’s main active substance, does more to your circadian rhythm than you can ever imagine.

A late cup of coffee can mess your sleep in more than a single way: Caffeine doesn’t only keep you awake, but it also messes up the internal body clock. This basically means that caffeine changes the way your body decides to sleep or wake up.

Kenneth P. Wright Jr., a co-author of recently published study and director of Sleep and Chronobiology Laboratory at the University of Colorado, says that caffeine “affects our physiology in a way we hadn’t really considered in the past”. Such discovery may affect night owls who’d like to get up earlier, or those who experience a jet lag after a long and tiresome travel between the time zones.

In the published study, five healthy individuals have spent a night in a laboratory, where the researchers have monitored their melatonin levels, a hormone responsible for our circadian rhythm. Melatonin is a natural indicator of circadian rhythm, where high levels suggest that body needs to rest and go to sleep.

Three hours before the sleep, the participants would take either a caffeine pill which contained an amount of caffeine worth of two espresso shorts, or a placebo pill. The participants who had taken a caffeine pill previously would take the placebo pill the night after, and vice versa.

The study has shown that the caffeine pill delays the release of melatonin for at least 40 minutes. This basically means that caffeine affects the body’s internal clock, pushing the biological night later.  It is widely known that caffeine releases the chemicals which promote arousal and wakefulness, but the recent study suggests that circadian rhythm is affected as well.

A delay of melatonin’s release could have a huge impact on a person’s body. For example, if an individual is exposed to a bright light just before the bedtime, such factor could delay the release of melatonin by 85 minutes. Further research of caffeine’s effects on circadian rhythm may be available anytime soon, as this study creates a good base for later examinations.

The study was published on Sept. 16, in journal Science Translational Medicine.