Your afternoon pick-me-up may have some unintended consequences.
Caffeine can make it more difficult to fall asleep and stay asleep since it competes with adenosine, a naturally occurring chemical in the body that promotes drowsiness.
Most experts agree that we should observe a caffeine cut-off so our coffee or soda habits don’t mess with our snoozing — but if you think giving it up a few hours before bedtime is enough, you may want to think again.
Researchers in Australia looked at the effects of caffeine consumption in coffee and pre-workout supplements (of which caffeine is often an ingredient) and how it contributes to insufficient sleep.
Analyzing 24 studies, they concluded that coffee should be consumed at least 8.8 hours prior to bedtime to avoid consequences for your rest.
That means if you go to bed at 10 p.m., your last cup of joe should be before 1:12 p.m.
Meanwhile, your last standard serving of pre-workout supplement — which has twice the caffeine of coffee — should be consumed at least 13.2 hours before sleep. For that 10 p.m. bedtime, that means before 8:48 a.m.
Drinking caffeine closer to bedtime shaved 45 minutes off the total sleep time and also increased sleep onset latency — the length of time it takes to transition from full wakefulness to the lightest stage — by 9 minutes.
Wake after sleep onset, or the total amount of time someone spends awake after falling asleep and before waking for the day, increased by 12 minutes.
There was also a 7% reduction in sleep efficiency, the amount of time actually spent asleep compared to the amount of time physically spent in bed.
Published in the journal Sleep Medicine Reviews, the research also looked at how caffeine consumption affected sleep stages.
Where caffeine was consumed closer to going to sleep, light stage sleep increased, while deep sleep decreased.
Meanwhile, of the 24 studies analyzed, 10 looked at the effects of caffeine on rapid eye movement (REM) stage sleep. However, no significant effects were demonstrated.
Not only did the amount and timing of the last caffeine intake reduce total sleep time, but the closer to bedtime higher doses of caffeine were consumed, the greater the reduction in subsequent sleep.
For example, drinking caffeine at 3 p.m. before a 10 p.m. bedtime would result in 16 minutes less sleep than consuming coffee or an energy drink at 9 a.m.
The one source of caffeine that didn’t have much of an impact on sleep?
Black tea, with research showing that one 250-milliliter cup (containing 47 milligrams of caffeine) could be consumed right up until bedtime and not affect sleep.
While around 80% of US adults consume caffeine every day, the first sip is the strongest.
Within 45 minutes of consumption, 99% of caffeine is absorbed by the body. But the amount of time it takes your system to reduce it to half of its original amount — the half-life — ranges from 1.5 to 9.5 hours.
However, everyone metabolizes caffeine differently, partly due to genetics, which explains why some people can down a cup of coffee and drift off to sleep almost immediately.
Caffeine also disrupts the natural process of adenosine collecting in the body throughout the day to help to regulate sleep-wake cycles, thereby keeping you wide awake when it comes time for shut-eye.
Experts also advise delaying your first cup of coffee till 90 minutes after waking to help balance hormones, particularly cortisol, the body’s primary stress hormone.
