A Cup of Joe Cannot Replace Adequate Sleep

If you didn’t get enough sleep last night, you may be relying on a cup of Joe (or two) to get you through the morning. Instant, percolated or pressed – with cream, sugar or just plain black – coffee is one of the most popular drinks in the world, and we are counting on it to perk us up.  How exactly does it work? Sleepiness comes from a brain chemical called adenosine; adenosine builds throughout the day, giving you that tired, sleepy feeling. When you finally get some sleep, adenosine is removed from your system and the cycle repeats. So what do you do when that 2 pm slump hits and you can’t stop for a nap -- drink a cup of coffee and ward of sleepiness. The caffeine in your cup of Joe helps repel adenosine molecules from reaching the brain’s receptors, preventing that tired, sleepy feeling. New research, however, finds the even the magic of caffeine may have its limits.

A recent double blind, placebo-controlled study looked at whether caffeine is sufficient to prevent performance decline after long-term sleep restriction. The study included 48 healthy individuals. The participants were randomly assigned to two groups: the intervention group and the control group. Participants in the intervention group were administered 200 mg of caffeine twice daily, while participants in the control group received a placebo twice daily. Participants in both groups restricted sleep to five hours per night for a total of five days. Participants underwent cognitive testing six times per day throughout the five-day period. Testing included a psychomotor vigilance task (PVT) test (measures reaction time), Profile of Mood States (POMS) and the Stanford Sleepiness Scale (SSS).

Results showed that relative to the placebo, caffeine significantly improved PVT performance during the first two days, but not the last three days of sleep restriction. Lead author Tracy Jill Doty, PhD, states, "These results are important, because caffeine is a stimulant widely used to counteract performance decline following periods of restricted sleep. The data from this study suggests that the same effective daily dose of caffeine is not sufficient to prevent performance decline over multiple days of restricted sleep.”

Bottom Line: The recommended amount of sleep is seven to eight hours per night, but as many as 40 percent of Americans are getting less than seven hours of sleep. With a packed schedule, sleep often moves to the bottom of the priority list. This study is an important reminder that adequate sleep should be considered a necessity, not a luxury. While that cup of coffee may add pep to your step over the short term, your performance may start to suffer if restricted sleep becomes a habit. If you’re not currently getting the recommended seven to eight hours, try setting a consistent bed time for yourself that is at least 30 minutes earlier than when you typically hit the hay. Use that thirty minutes to unwind and unplug to promote a restful night’s sleep.


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