“[Sleep-deprived people] can call on cognitive resources they have that they normally don’t need to use to do a certain task. That allows them to perform reasonably well, but they still don’t perform at normal levels,” says researcher Sean P.A. Drummond, PhD, associate professor of psychiatry at the University of California San Diego and the VA San Diego Healthcare System.
Your body clock also will give you a periodic boost, as it triggers a wake signal in your brain. You may feel a second wind in the mid-morning (around 10 a.m.) and again in the early evening (at 6 p.m. or 7 p.m.). “You may feel better, but you’re still likely to be forgetful, slower to react, and less attentive," Dinges says.
Fortunately, there are some things you can do to improve your alertness and make it through the day after.
Take a Nap
The antidote to sleeplessness is sleep, says Rosekind, who led a fatigue management program for the National Aeronautics and Space Administration (NASA). In a study led by Rosekind, pilots on transpacific flights who napped for an average of 26 minutes had 34% fewer performance lapses and were half as likely to show signs of physiologic sleepiness.
Even a nap as short as 10 minutes can benefit you, as your brain quickly moves into slow-wave sleep, Dinges says. If you sleep longer than about 40 or 45 minutes, you may feel groggy when you wake up. This is called sleep inertia, and happens when you wake from a deep sleep. Once you shake off that feeling, you’ll benefit from the nap and feel sharper than you would have without it, Dinges says.
Drink Coffee or Another Caffeinated Beverage
Be strategic with your coffee or energy drink and you’ll get an extended boost in alertness. Most people need about 100 milligrams (mg) to 200 mg of caffeine, depending on their body weight, Rosekind says. (Coffee has about 100 mg of caffeine in a 5-ounce cup, though the content varies based on the strength of the brew.) Over-the-counter caffeine pills also are available in 100 mg or 200 mg doses.