Catch up sleep, avoid caffeine
2006-10-14 12:01
New York - Caffeine has a stronger disruptive effect on daytime, catch-up sleep after a night of sleep deprivation than it does on a normal night's sleep, according to a new study.
"Recent studies have suggested that caffeine is a measure of choice to counteract the effects of sleep deprivation on alertness and performance," wrote Dr Julie Carrier of the Hopital du Sacre-Coeur de Montreal in Quebec, Canada.
"Our results suggest this recommendation should be made with caution, since using caffeine before sleeping at an abnormal circadian phase, such as during night work, might have more adverse consequences on sleep quality than before sleeping at a normal circadian time."
Carrier and her team noted that consuming caffeine at night was known to make it more difficult to fall asleep and to worsen sleep quality.
They hypothesised that caffeine would have an even stronger effect when people were trying to recover from sleep deprivation by snoozing during the day.
To investigate, they had 34 people consume caffeine or a placebo before going to sleep at their normal bedtime.
A month later, the same individuals were then deprived of sleep for an entire night, after which they were instructed to fall asleep an hour after their normal wake-up time, again after being given placebo or caffeine.
Caffeine 'doesn't affect REM'
People received 100mg of caffeine or placebo before their scheduled morning or evening bedtime, and then another 100mg (or placebo) one hour before.
Researchers found that all study participants who took caffeine took longer to fall asleep and spent more time in lighter stage one sleep and less time in deeper stage two and slow-wave sleep.
But people given caffeine before daytime sleep took even longer to drop off, and also slept for a shorter time and had less REM sleep. Caffeine didn't affect night time sleep duration or REM.
Carrier and her colleagues suggested the greater daytime effects of caffeine were because people were trying to fall asleep at a time when their body clock was telling them to stay awake, even though they were sleep-deprived.
They said slow-wave sleep was known to last longer during daytime, catch-up sleep, which normally helped override this circadian signal.
Given that caffeine reduced slow-wave sleep, it appeared to allow the wake-up call to remain strong, read the study.