Is a daytime power nap healthy or not?
A power nap of less than 30 minutes taken early in the afternoon provides a modest but measurable boost to alertness and concentration, without the health risks associated with longer naps. For most people, such a short nap does not disrupt night-time sleep either.
A nap averaging 55 minutes early in the afternoon provides a small to moderate boost to alertness, memory and concentration, lasting about two hours. This holds across all ages and sexes. However, almost all of this research was conducted in a laboratory setting, so whether the same benefits apply in a typical workplace is not certain.1
Immediately after waking you may experience sleep inertia: a groggy feeling that temporarily lowers your performance. This passes on its own, but you should therefore not schedule a nap just before a meeting or task. The improvement in alertness only kicks in afterwards.1
Naps of 30 minutes or longer are a different matter. A meta-analysis of 44 large population studies involving more than 1.8 million participants shows that long naps are associated with higher mortality, more cardiovascular disease and more diabetes. Naps under 30 minutes do not show this elevated risk. Because these are observational studies, it is also possible that people who take long naps are already in poorer health.2
Two genetic studies with a combined total of more than 800,000 participants from the UK Biobank make a genuine causal relationship more plausible. People with a genetic predisposition to napping more frequently had higher blood pressure and a larger waist circumference, even after correcting for weight. These are risk factors for cardiovascular disease.3,4
The same large meta-analysis hints at a benefit of napping in older age: less cognitive decline and less muscle weakness. However, the evidence is limited and a causal relationship has not yet been established. The advice to avoid naps in order to improve night-time sleep is, incidentally, less well supported than it sounds; outside the clinic it has barely been tested. People who sleep well at night do not necessarily need to cut out a short nap of under 30 minutes.2,5
The evidence for cognitive improvement comes from a meta-analysis of laboratory studies (PMID 34639511). The health risks have been examined in a large meta-analysis of population studies (PMID 39153335) and two genetic studies in the UK Biobank (PMID 33568662, 37925459). The sleep hygiene advice is observational and has limited supporting evidence (PMID 25454674).
What does a daytime nap do to your health?
A short nap of less than 30 minutes appears safe and good for alertness. People who regularly nap for longer than half an hour show higher risks of elevated blood pressure, diabetes and cardiovascular disease in the research. So keep it short if you nap during the day.
Is it a problem that I often wake up during the night?
Waking up occasionally is normal, but if it happens frequently and affects you during the day, there may be an underlying cause such as sleep apnea or PTSD. In that case, have it checked out.
Is sleeping in on the weekend beneficial, or does it fail to make up for sleep deprivation?
Sleeping in on the weekend temporarily relieves fatigue but does not genuinely make up for sleep deprivation: cognition, weight and diabetes risk do not improve as a result. Consistency in sleep timing has more impact than a catch-up attempt on Saturday.
Does walking outside during the day help me sleep better at night?
A daily walk of around half an hour outside helps improve your sleep, as shown by a randomised study. The surroundings matter little, but air pollution can dampen the effect.
Is it true that sleep before midnight is better than sleep after midnight?
The time before or after midnight is not the real criterion: what matters is how well your sleep timing aligns with your own biological clock. Sleep at the wrong time for your rhythm and quality drops, but for a night owl that can simply mean going to bed late.
How harmful is irregular sleep or shift work, and what can you do about it?
Shift work is demonstrably harmful to sleep, alertness and metabolism. The best approach combines a well-designed schedule with forward rotation, strategic use of light, melatonin and, where appropriate, cognitive behavioural therapy.