Sleep

The coffee nap: why caffeine and a short nap work well together

Drink a coffee, then nap for 15 to 20 minutes. You wake up just as the caffeine starts to work, often feeling sharper than with either alone.

A coffee nap sounds like a contradiction, but it makes sense once you know the timing. Caffeine takes roughly 20 to 30 minutes after drinking to reach meaningful levels in the blood and start blocking adenosine, the chemical that builds up while you are awake and makes you feel sleepy. A short nap also clears some adenosine. If you drink coffee and immediately lie down for 15 to 20 minutes, you wake up with less adenosine and caffeine arriving just in time.

Small studies, including tests on tired drivers, found that combining caffeine with a brief nap improved alertness and performance more than caffeine alone or a nap alone. The nap has to stay short. Longer than about 20 to 30 minutes and you are more likely to enter deep sleep, which leaves you groggy on waking. Even if you do not fall asleep fully, lying quietly with your eyes closed still seems to help.

The coffee nap is useful before an afternoon training session after a short night, before a long drive or during a post-lunch slump. Drink the coffee quickly rather than sipping it for half an hour, set an alarm for 20 minutes and nap in a dark, quiet place if possible. Avoid it late in the day: caffeine stays in the body for many hours, and a coffee at 5 p.m. can still disturb sleep at midnight. It is a tool for occasional tired days, not a replacement for enough nighttime sleep.

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