How naps can help or harm your night-time sleep

By mid-afternoon, your eyelids may feel heavy and your concentration can begin to fade. You take a 30-minute nap and wake feeling restored. Yet, when bedtime arrives, you are lying awake and wondering why sleep will not come. That refreshing daytime nap may be the cause.

Naps are often celebrated for increasing alertness, lifting mood, reinforcing memory and raising productivity. For certain people, however, they can undermine sleep at night.

Napping has both benefits and drawbacks. Used properly, it can refresh the brain, sharpen concentration and promote mental and physical wellbeing. Taken at the wrong time or for too long, it may leave you sluggish, confused and unable to fall asleep later on.

The answer depends on how the body controls sleep and wakefulness.

Why naps can affect night-time sleep

Most people have a naturally occurring fall in alertness during the early afternoon, usually from 1 pm to 4 pm. A substantial lunch is not the only explanation: the body’s internal clock, known as the circadian rhythm, produces repeating periods of wakefulness and fatigue across the day. The early-afternoon dip forms part of that pattern, which explains why drowsiness is so common then.

Evidence indicates that a brief nap at this time - ideally with exposure to bright light afterwards - may reduce tiredness, increase alertness and support cognitive performance without disrupting night-time sleep. These "power naps" give the brain a break without allowing it to enter deep sleep, so waking up refreshed is easier.

There is a downside, though: a nap that lasts too long can make you feel worse than you did beforehand. The reason is "sleep inertia" - the grogginess and disorientation caused by waking during the deeper stages of sleep.

After a nap goes beyond 30 minutes, the brain moves into slow-wave sleep, from which waking is considerably more difficult. Research shows that people roused from deep sleep can remain sluggish for as long as an hour.

That may have major consequences when someone needs to undertake safety-critical work, make significant decisions or use machinery, for instance. A nap taken too late can also reduce the build-up of ‘sleep pressure’ - the body’s natural need for sleep - making it more difficult to fall asleep at night.

When napping is essential

For some people, naps are necessary. Shift workers frequently contend with broken sleep because of irregular timetables, and a carefully timed nap before a night shift can improve alertness while lowering the likelihood of mistakes and accidents.

Likewise, people who consistently do not get sufficient sleep overnight - because of employment, parenting or other pressures - may use naps to store additional sleep hours and offset their lost sleep.

Even so, using naps in place of improving night-time sleep is a temporary measure, not a lasting answer. Those with chronic insomnia are commonly advised not to nap at all, since sleeping during the day can lessen their drive to sleep at night.

Strategic naps for performance

Some groups use planned napping to enhance performance. Athletes build naps into training programmes to accelerate muscle recovery and improve sporting measures including reaction time and endurance.

Research further indicates that workers in roles demanding intense focus, including healthcare staff and flight crews, gain from short scheduled naps that help preserve concentration and limit fatigue-related errors. NASA has found that a 26-minute nap can improve performance of long-haul flight operational staff by 34 percent, and alertness by 54 percent.

How to nap well

Both timing and surroundings are important for an effective nap. Restricting a nap to between ten and 20 minutes helps avoid grogginess. It is best to nap before 2 pm, as doing so later may delay the body’s natural sleep routine.

The most effective naps are taken somewhere cool, dark and quiet, much like the conditions for sleeping at night. Eye masks and noise-cancelling headphones can be useful, especially for people napping in noisy or brightly lit places.

For all its advantages, napping does not suit everyone. Whether it helps or hinders depends on age, lifestyle and existing sleep habits. A successful nap requires a strategy: understanding whether to nap at all, as well as when and how to do it.

For some people, it is a life hack that boosts energy and focus. For others, it can become a route towards disturbed sleep. The important thing is to try it and monitor the effect naps have on your overall sleep quality.

When used thoughtfully, naps can be a useful resource. When handled badly, they may be why you are staring at the ceiling at midnight.

Talar Moukhtarian, Assistant Professor in Mental Health, Warwick Medical School, University of Warwick

This article is republished from The Conversation under a Creative Commons licence. Read the original article.