The perfect nap: how long it should last and when to take it to wake up refreshed

After lunch your eyelids get heavy, your focus drops and the couch seems to be calling your name. In many Latin countries the siesta is almost an institution; elsewhere it is still seen as a sign of laziness. Sleep science, however, has studied napping in depth, and its conclusion is clear: a well-timed nap can be a great ally, but how long it lasts and when you take it make all the difference.

Why we feel sleepy after eating

Many people blame the food, but that is not the only reason. Our body clock, the circadian rhythm, has a small natural dip in alertness in the early afternoon, roughly between 1 p.m. and 4 p.m. It happens even in people who have skipped lunch. A heavy meal, a fatty one or one with alcohol, combined with a poor night’s sleep, can make that dip much stronger.

The word «siesta» comes from the Latin hora sexta, the sixth hour of the day counted from dawn, which corresponded more or less to midday. In other words, the habit of resting at that time is very old.

The NASA experiment

One of the most cited nap studies was carried out in the 1990s with long-haul commercial airline pilots. Researchers at NASA’s Ames Research Center allowed one group of pilots a 40-minute rest period in the cockpit during the quiet cruise phase of the flight, while another pilot stayed in control. On average, those who rested slept for about 26 minutes.

The results were striking: the napping group showed significant improvements in reaction times and alertness measures compared with the group that did not rest, and had fewer episodes of microsleep toward the end of the flight. Since then, the phrase «NASA nap» has been used to describe short, strategic naps.

How long it should last

Most specialists recommend naps of 10 to 20 minutes for everyday use. At that length we usually stay in the lighter stages of sleep, and it is easy to wake up with a clear head.

If a nap stretches to 30 or 60 minutes, the chance of slipping into deep sleep rises. Waking up from that stage brings what is known as sleep inertia: that groggy, clumsy, irritable feeling that can last quite a while. That is why a long nap sometimes leaves you feeling worse than before.

A nap of around 90 minutes can complete a full sleep cycle, including REM sleep, which can help if you slept very little the night before, but it can also make it harder to fall asleep at night.

When to nap

Ideally, take advantage of the natural afternoon dip, shortly after lunch, and avoid sleeping late in the afternoon. A late nap reduces the «sleep pressure» that builds during the day and can make it harder to fall asleep at night. People with insomnia are often advised to skip naps or keep them very short.

Is it good for your heart?

Here the studies are observational: they find associations but do not prove cause and effect. A Greek study published in 2007 found that people who napped regularly had lower coronary mortality. A Swiss study from 2019 observed that people who napped once or twice a week had fewer cardiovascular events than those who never napped.

On the other hand, several studies have linked very long naps, of more than an hour a day, with a higher risk of metabolic and cardiovascular problems. Spanish research published in 2023 associated naps longer than 30 minutes with higher body mass index and more metabolic syndrome, while short naps did not show that effect. In some cases, needing a lot of daytime sleep may be a sign of a health problem or poor night-time sleep rather than the cause.

The coffee-before-a-nap trick

Some studies have tested the so-called «coffee nap»: drinking a coffee just before a nap of about 15 to 20 minutes. Because caffeine takes a while to kick in, it starts working roughly when you wake up. In small experiments, this combination improved alertness more than the nap alone. It is not a good idea, though, if you already consume a lot of caffeine or if the nap is late in the day.

Tips for a good nap

• Set an alarm so you do not go past 20 or 30 minutes.
• Find a quiet place with dim light and a comfortable temperature.
• If you cannot lie down, reclining in an armchair works too.
• Do not rely on naps to make up for short nights all the time: night-time sleep is still what matters most.
• If you feel excessively sleepy during the day even though you sleep well, see a doctor: sleep apnea or another disorder may be involved.

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