Drinking coffee before bedtime disrupts body’s internal clock: Study
19 Sep 2015
Drinking coffee before bedtime disrupted the body's internal clock, and made it harder to get to sleep on time. It also made it more challenging to wake up in the morning, researchers from the University of Colorado at Boulder.
The findings in the journal Science Translational Medicine not only explained the reason behind caffeine-drinkers staying up and waking up late, but it could also offered travellers a way to time their caffeine use to limit the effects of jet lag, according to researchers.
The study involved five randomly selected volunteers who were asked to consume as much caffeine as was contained in a double espresso three hours before bed, or who were exposed to bright lights, or were given a placebo.
Volunteers were observed in the study for 49 days and their saliva was regularly tested for levels of the hormone melatonin, which naturally regulated sleep and waking cycles.
The researchers found that those who took caffeine in low-light conditions experienced about a "40-minute phase delay of the circadian melatonin rhythm," said the study.
Volunteers who were exposed to overhead lights three hours before bed had their circadian clocks set back by 85 minutes, while those who took both the caffeine and sat under bright lights were disrupted by 105 minutes.
Joint lead researcher Dr John O'Neill, from the Medical Research Council Laboratory of Molecular Biology in London said, "The effect of caffeine on sleep and wakefulness has been long established, but its impact on the underlying body clock has remained unknown.
"These findings could have important implications for people with circadian sleep disorders, where their normal 24 hour body clock doesn't work properly, or even help with getting over jet lag.
"Our findings also provide a more complete explanation for why it's harder for some people to sleep if they've had a coffee in the evening - because their internal clockwork thinks that they're an hour further west.
"By understanding the effect caffeinated drinks have on our body clock, right down to the level of individual cells, gives greater insight into how we can influence our natural 24 hour cycle, for better or for worse."
