Chronic insomniacs will have heard these messages before: “Don’t nap.” “Avoid caffeinated beverages later in the day.” These are good rules of thumb for most people with insomnia. If you catch yourself drifting off during the 6 o’clock news, it’s better to get up and walk around the block than drink coffee or indulge in a full-blown nap.
But some situations warrant breaking the rules. Say you end up pulling an all-nighter to study for a test and have to take a second test later the same day. Or say a family crisis triggers a couple bad nights and the next night you have to drive all the way to St. Paul. If you’ve got to be on your toes despite feeling seriously sleep deprived, then napping and well-timed use of caffeine make sense. Here’s what the research says.
Turning Low Energy into High
It’s normal to feel low energy when you’re short on sleep, and nerve-wracking when the situation calls instead for stamina and alertness. Your first impulse may be to reach for an energy drink. Energy drinks usually deliver what they promise: studies show that caffeine—a main ingredient—can improve attention, reaction speed, information processing, memory, mood, and aerobic performance.
Caffeine quickly moves from your gastrointestinal tract into your bloodstream. It’s at peak strength about 1 hour after you drink it. Caffeine blocks secretion of adenosine, in turn increasing the release of neurotransmitters that promote arousal. Fatigue falls away and your brain comes alive again.
When Caffeine Isn’t Enough
But under conditions of extreme sleep deprivation, caffeine by itself doesn’t work very well. Researchers at the University of Pennsylvania confirmed this and found out more when they conducted a double-blind study on sleep-deprived subjects to compare the effects of caffeine with and without periodic naps.
The participants, 58 healthy men (average age 29), underwent 3 nights of total sleep deprivation. Starting at hour 22, half of the men took a low-dose caffeine pill every hour on the hour, and the other half took a placebo. Half of the caffeine takers were also allowed to take a 2-hour nap every 12 hours and the other half were not. Likewise for the placebo takers.
The participants were tested repeatedly, and here’s what the investigators saw in the group taking only low-dose caffeine:
- Compared with placebo, the caffeine significantly reduced declines in reaction time and lapses in attention associated with sleep loss, but this effect fell off as participants grew more and more sleep deprived.
- Compared with placebo, caffeine did nothing to increase the amount of information the sleep-deprived participants could process or improve their working memory.
Adding Naps to Reduce Fatigue & Improve Performance
But taking low-dose caffeine and a 2-hour nap every 12 hours improved participants’ attention, ability to process information, and working memory. These effects held steady through all 3 days of the study. Adding caffeine to the naps also reduced the drowsiness participants felt on awakening from their naps.
The Penn researchers point out that “caffeine at any dose is not a chemical substitute for adequate healthy sleep.” But in situations where people must perform under conditions of sleep deprivation, “brief naps in combination with properly-dosed and well-timed energy products containing caffeine may provide the most benefit.”
Some people with insomnia don’t have an easy time napping, and I’m one of them. But when I’m truly suffering sleep loss—say, when I have jet lag on returning home from a trip—and I have to be up and alert, I turn on the coffee maker, nap if I can, and drink my coffee immediately on waking up.
But Note These Caveats
The effects of caffeine vary greatly from person to person largely due to genetic factors:
- In this experiment, for example, the peak concentration of caffeine in the blood plasma of participants ranged from 2.0–9.4 mg/l. That’s a very wide range. It suggests that some participants’ behavior was much more impacted by caffeine than others’.
- Also, some people metabolize caffeine more slowly than others. On average, caffeine has a half-life of 5–6 hours. But its half-life ranges from 2.5–10 hours (and the range is even wider in people who are pregnant, taking antidepressants, or have liver disease). A particular genetic polymorphism causes more women to metabolize caffeine more slowly than men, and more Asians and Africans to metabolize caffeine more slowly than Caucasians.