Coffee and Sleep: It’s Complicated

If you’re like most people, you may associate coffee and other caffeinated beverages with waking up with zip, and jumpstarting your day. You also may assume that post-dinner espresso is a bad decision, if you’re looking for a solid night’s rest that is. But some studies suggest that it’s not so cut and dry; that caffeine’s effect on your body is inherently driven by your DNA’s unique chronotype. And caffeine has different effects on morning people and “night owls”, as shown by different sleep patterns.

Your chronotype is your internal system that dictates your body’s natural rhythms and energy cycles throughout the day. It’s your body’s way of taking charge and saying, “Dang, it feels good to get up and see the sunrise!” or “Don’t talk to me before 10 a.m.” And we all know people who fall into both camps.

How caffeine affects morning people

Morning folks may have no problem waking early and consuming caffeine in the daytime. But once it’s time to sleep, unfortunately, they may be left tossing and turning the night away.  In one study, 50 college students recorded their caffeine consumption and sleeping and waking schedules for a full week. The students had their saliva tested regularly to check for caffeine levels. Additionally, each wore a special wrist device that recorded every movement. These devices looked for periods of wakefulness after they went to sleep.

Researchers ran into an interesting challenge with college students: most of them crashed hard regardless of their caffeine intake, since they were sleep deprived for most of the time regardless. However, researchers noticed a peculiar behavior in the early riser group: there was a direct correlation between levels of caffeine and wake time throughout the night. In other words, the more caffeine they took in during the day, the more they woke up throughout the night.

Another interesting find: everyone’s body processes caffeine at a unique rate. The researchers saw that “some people’s bodies clear caffeine within a few hours, but lunchtime coffee may still be in the system of other people even late at night. Therefore it’s hard to say whether any particular person could avoid the effects of caffeine on sleep by simply steering clear of coffee (or tea) in the afternoon or evening.”

Know your body’s patterns.

This study offers yet another round of evidence that our body’s cycles are often more complex than we give them credit. We’ve been following canned advice on how to go about our days and get optimal sleep—stick to a schedule, exercise in the morning, coffee is “bad”.

But sleep isn’t a one-size-fits-all thing. And neither is how our body processes caffeine. Knowing your body’s unique chronotype and your patterns of wakefulness and sleepiness will not only improve your zzz’s, it could help improve almost every area of your life, from optimizing your workout schedule to knowing the best time to study.