For years, napping has been derided as a sign of laziness. We are "caught" napping or "found asleep at the switch". But lately it has garnered new respect, thanks to scientific evidence that midday dozing benefits both mental acuity and overall health. A slew of recent studies have shown that naps boost alertness, creativity, mood, and productivity in the later hours of the day.
A nap of 60 minutes improves alertness for up to 10 hours. Research on pilots shows that a 26-minute "Nasa" nap in flight (while the plane is manned by a copilot) enhanced performance by 34% and overall alertness by 54%. One Harvard study published last year showed that a 45-minute nap improves learning and memory. Napping reduces stress and lowers the risk of heart attack and stroke, diabetes, and excessive weight gain.
Naps make you brainier, healthier, safer. But to understand how you can nap best, you need to understand your body.
How long should you rest for?
A short afternoon catnap of 20 minutes yields mostly Stage 2 sleep, which enhances alertness and concentration, elevates mood, and sharpens motor skills. To boost alertness on waking, you can drink a cup of coffee before you nap. Caffeine requires 20 or 30 minutes to take effect, so it will kick in just as you're waking. Naps of up to 45 minutes may also include rapid eye movement (REM) sleep, which enhances creative thinking and boosts sensory processing.
Limit your nap to 45 minutes or less, if you need to spring into action after dozing. Otherwise, you may drift into slow-wave sleep. Waking from this stage results in sleep inertia, that grogginess and disorientation that can last for half an hour or more.
Why do we need to nap?
Most mammals sleep for short periods throughout the day. Humans have consolidated sleep into one long period, but our bodies are programmed for two periods of intense sleepiness: in the early morning, from about 2am to 4am, and in the afternoon, between 1pm and 3pm. This midday wave of drowsiness is not due to heat or a heavy lunch (it occurs even if we skip eating) but from an afternoon quiescent phase in our physiology, which diminishes our reaction time, memory, coordination, mood, and alertness.
Are you a lark or an Owl?
To determine the best time to nap, it helps to know your "chronotype". What time would you get up and go to sleep if you were entirely free to plan your day? If you're a lark, apt to wake as early as 6am and go to sleep around 9pm or 10pm, you're going to feel your nap need around 1pm or 1.30 pm.
If you're an owl, preferring to go to bed after midnight or 1am, and to wake around 8am or 9am, your afternoon "sleep gate" will open later, closer to 2.30pm or 3pm.
Excerpted from Jennifer Ackerman's article “Napping: the expert’s guide” published in The Gardian, Monday, January 26, 2009.