Are Power Naps Good for You? What the Evidence Shows

A short nap can feel like a reset button. Twenty minutes on the sofa and the afternoon fog lifts, and the next few hours run smoother. That everyday experience holds up in controlled trials. In a pooled analysis of eleven of them, a daytime nap measurably improved alertness and cognitive performance in the hours that followed.

There is a second half to the story that gets less attention. The same habit, taken too long or leaned on too hard, tracks with poorer health in large population studies. Long daytime naps are linked to higher rates of heart disease and earlier death, though the direction of that link is not as simple as it first looks. Get the length and timing right and a nap is a low cost way to sharpen a tired afternoon. Get them wrong and you wake groggier than before. Here is what the evidence shows, and how to nap in a way that helps.

What a short nap does for the brain

The clearest evidence on the benefits comes from a 2021 systematic review and meta-analysis in the International Journal of Environmental Research and Public Health. Dutheil and colleagues pooled eleven controlled trials with 381 adults, comparing a daytime nap against staying awake. Overall cognitive performance improved after the nap, with an effect size of 0.18. Alertness improved the most, at 0.29. Memory showed a smaller change, 0.11, that was not clearly above zero.

An effect size is a way to compare results measured on different scales in different studies. An effect near or above 0.2 counts as small but genuine, so the overall figure of 0.18 sits just under that low bar and the alertness figure of 0.29 clears it comfortably. In plain terms, a nap will not make you a different person, but it reliably takes the edge off an afternoon slump and helps you think a bit more clearly. The improvement lasted for up to about two hours after the nap. Naps taken before one in the afternoon worked better for cognition than later ones. The chart below sets the three outcomes side by side.

Data: Dutheil and colleagues (2021), meta-analysis of 11 trials, 381 adults. Alertness showed the largest and clearest benefit.

The sweet spot is short and early

How long you nap changes the result more than anything else. Guidance from the CDC and NIOSH, written for shift workers who need to stay sharp, is to set an alarm for 15 to 30 minutes. A brief nap raises alertness for a couple of hours afterwards, with less grogginess, and it does not disrupt sleep at night. That is the version of a nap most people are chasing.

The reason the clock matters is what happens as sleep goes on. It moves through lighter stages first and reaches its deepest phase, slow wave sleep, in about one hour. If you wake out of that deep stage, your functioning can dip sharply for a while, a state called sleep inertia. That is the heavy, disoriented feeling after a long nap. A 20 minute nap keeps you in lighter sleep and lets you wake near where you started, only fresher. A nap that stretches toward an hour or beyond risks waking you as deep sleep takes hold, which is why a long nap can leave you worse than no nap at all. Timing helps too. An early afternoon nap lines up with the natural post lunch dip in alertness and sits far enough from bedtime to leave your night sleep alone.

The catch with longer naps

The health headlines come from a different kind of study. A 2026 umbrella review in Public Health Reviews by Du and colleagues gathered 16 meta-analyses of daytime napping and health. Across that pooled evidence, daytime napping was associated with worse outcomes on several conditions. Compared with people who did not nap, regular nappers had roughly 19% more hypertension, 20% more type 2 diabetes, 22% higher all cause mortality, 30% more coronary heart disease, and 47% more stroke in the pooled data.

Two things stop this being a reason to skip your afternoon rest. First, the risk clustered around long naps. Naps of 60 minutes or less showed no clear link with earlier death, while the raised risk sat with naps beyond an hour. Second, and more important, these are associations from observational data, not proof that napping causes harm. Poor night sleep, and illness that has not yet been diagnosed, both make people nap more and for longer during the day. So a long daily nap can be a signal of an underlying problem rather than the cause of one. The honest reading is that short, early naps look safe and useful, while a pattern of long, frequent naps is worth paying attention to, both as a possible marker of poor health and as a habit that tends to erode night sleep. The chart below shows the size of each association.

Data: Du and colleagues (2026), umbrella review of 16 meta-analyses. Figures are relative risks and odds ratios from observational studies, so they show association, not cause.

Short nap or long nap

Put the two halves together and the practical difference between a short nap and a long one is stark. One is a tool. The other is either a treat that leaves you foggy or a warning sign worth reading.

Length is the main lever. Keep a nap short to get the benefit without the downsides.

How to nap well

A good nap takes a little planning. These four steps line up with what the trials and the health guidance point to, and they keep the effort where it pays off.

Common mistakes

A few habits turn a helpful nap into a drag on the day. The first is the long catch up nap that runs past an hour and leaves you heavy and slow for the rest of the afternoon. The second is napping late in the day, then lying awake at night because the pressure to sleep has been spent. The third is leaning on a daily long nap to paper over short or broken night sleep, which treats the symptom and leaves the cause untouched. The fourth is spending the window on a phone rather than resting, so the body gets little chance to switch off. Keep naps short, early, and screen free, and they earn their place.

Frequently asked questions

The bottom line

A short, early nap is a genuine tool for a tired afternoon. Keep it to 15 to 30 minutes, take it soon after lunch, and wake before deep sleep so you rise sharper rather than groggier. The health worries in the headlines attach to long, frequent naps, and much of that link reflects poor night sleep or hidden illness rather than harm from the nap itself. Use a nap to top up a good night, not to stand in for one, and it becomes a small, reliable part of feeling and performing better.

Sources

• Dutheil F and colleagues (2021). Effects of a Short Daytime Nap on the Cognitive Performance: A Systematic Review and Meta-Analysis. International Journal of Environmental Research and Public Health. pmc.ncbi.nlm.nih.gov/articles/PMC8507757
• Du P and colleagues (2026). Multiple Health Outcomes of Daytime Napping: A Comprehensive Umbrella Review. Public Health Reviews. pmc.ncbi.nlm.nih.gov/articles/PMC12909254
• CDC and NIOSH. Training for Nurses on Long Work Hours: Napping, Nap Duration. cdc.gov