You probably know the feeling. A heavy afternoon rolls in, your eyelids get heavier, and the pull of a quick lie-down is hard to ignore. Most of us surrender without thinking about how long we should actually stay there.
The length matters far more than the fact that you napped at all. A 2026 umbrella review in Public Health Reviews pulled together 16 meta-analyses on daytime napping and health.
The researchers found that short naps help alertness and performance. Naps longer than an hour were linked to a 30 percent higher risk of coronary heart disease compared with people who did not nap.
The heart signal was not the only warning. Long naps were also tied to a 20 percent higher risk of diabetes and a 15 percent higher rate of death from any cause.
Also read: 8 warning signs of kidney stones most people mistake for back pain
Why 10 to 20 minutes hits the sweet spot
At this length, you drift into light sleep but never fall deep. The National Sleep Foundation describes the 15 to 20 minute power nap as the length that can restore and refresh you in the early afternoon.
Because you stay out of deep sleep, you wake up without the dazed, heavy feeling scientists call sleep inertia. That grogginess is the main reason longer naps often leave people feeling worse than before they lay down.
NASA has tested power napping as well, and the National Sleep Foundation notes the agency found it gave an effective boost to performance and alertness.
When 30 to 60 minutes gets complicated
At around half an hour, the brain starts entering slow-wave sleep. This is the deep, restorative stage. The trouble is that waking up in the middle of it is where the heavy, foggy feeling comes from.
Also read: How far should you be able to run without stopping? Distance sorted by age
The National Sleep Foundation flags medium naps of about 45 minutes as the problem zone. You are likely to wake during deep sleep, and the grogginess can wipe out any benefit the nap gave you.
A full 90-minute nap is a different case. It takes the brain through a complete sleep cycle and back into lighter stages, so you wake up more cleanly. For some people that helps memory and creativity, but it also eats into the next night's sleep.
Over an hour and the heart signal appears
Once a nap stretches past 60 minutes on a regular basis, the picture changes. The umbrella review flagged a consistent jump in cardiovascular, metabolic and mortality risk in people who habitually took long naps.
Naps of 90 minutes or more were tied to a roughly 50 percent higher risk of high blood pressure. The authors concluded that keeping daytime naps to an hour or less may be the best balance between benefit and risk for most adults.
Also read: Simple salt swap could prevent nearly 3 million deaths a year, study finds
Researchers cannot yet say that long naps cause heart disease. The pattern may partly reflect that people who feel the need for long daytime sleep are already less healthy. The warning sign shows up across studies either way.
The best time to nap and who should skip it
Timing matters almost as much as length. Most sleep researchers recommend napping before 2 p.m., so that the nap does not steal from the following night's sleep.
The window lines up with the natural afternoon dip in alertness. A short nap taken then tends to feel the most restorative and the least disruptive.
People with insomnia or trouble falling asleep at night are usually told to skip naps entirely.
Also read: What your nails can reveal about your heart, liver and thyroid health
If daytime sleep leaves you lying awake at midnight, the guidance in how to get the most out of a nap without ruining your nighttime sleep becomes the practical starting point before anything else.
For everyone else, the number the research keeps circling back to is simple. Set a timer for 20 minutes, lie down before 2 p.m., and get up when it goes off.
Also read: Smoked salmon recalled as FDA raises warning to highest risk level
This article is made and published by Mie Hermansen, who may have used AI in the preparation.