Key Message: Caffeine at night delays the circadian clock

Action Point: Removing coffee from your diet or just having one cup in the morning may help achieve earlier bedtimes and wake time
We all know that drinking caffeinated drinks before bed can disrupt sleep. But for the first time research suggests that your evening double espresso delays the internal circadian clock that tells us when to get ready for sleep and when to prepare to wake up.
A new study led by the University of Colorado Boulder and the Medical Research Council’s Laboratory of Molecular Biology in Cambridge, England shows that the internal clocks in human cells can be impacted by caffeine intake. According to Professor Kenneth Wright “this is the first study to show that caffeine, the most widely used psychoactive drug in the world, has an influence on the human circadian clock.”1
In the study, they compared what happened to people’s body clocks when they were exposed to caffeine three hours before bedtime to what happened when people were exposed to bright light at nighttime – which is already known to delay the body clock.
Researchers measured saliva levels of melatonin, which is a key hormone involved in regulating the body clock. It showed that drinking caffeine at night delays the body clock by 40 minutes. But it was found that the effect of caffeine is about half of what we see with light. The study showed that bright light alone and bright light combined with caffeine induced circadian phase delays in the test subjects of about 85 minutes and 105 minutes respectively.
The research suggests that not only will caffeine keep you awake longer at night but it could also push you into you into a whole new […]