How Much Sleep Do Adults Need? What the Evidence Says

"How much sleep do I need?" sounds like a simple question, and the headline answer really is simple: 7 or more hours for most adults. The interesting parts are why experts landed there, how much people differ, and what happens when you keep coming up short.

What do sleep experts recommend for adults?

In 2015, the American Academy of Sleep Medicine (AASM) and the Sleep Research Society (SRS) brought together a panel of experts to review the research. Their consensus, published in Sleep, was that adults aged 18 to 60 should sleep 7 or more hours per night on a regular basis to promote optimal health.

The panel added some nuance. Sleeping more than 9 hours a night may be appropriate for young adults, for people recovering from sleep debt, and for people who are ill. For other adults, the panel said it was uncertain whether regularly sleeping more than 9 hours is linked to health risk.

The National Sleep Foundation published a similar set of recommendations the same year in Sleep Health: 7 to 9 hours for adults aged 18 to 64, and 7 to 8 hours for adults 65 and older.

Note that these numbers mean hours asleep, not hours in bed. If it takes you 20 minutes to fall asleep and you wake briefly during the night, you need to be in bed for longer than 7 hours to get 7 hours of sleep.

Why at least 7 hours?

The recommendation comes from many kinds of evidence. Two are especially clear.

Short-term performance. In a 2003 lab study, healthy adults who spent 6 hours in bed a night for 14 nights showed steadily worsening attention, reaching levels seen after up to two nights without sleep. People kept to 8 hours in bed did not show this decline. The 6-hour group's own sleepiness ratings rose only slightly, so they largely did not notice how impaired they had become.

Long-term health. A 2010 meta-analysis in Sleep pooled 16 studies with more than 1.3 million people. Habitually short sleep was associated with a 12% higher relative risk of death over the follow-up period. Long sleep was also associated with higher risk, but researchers think that may partly reflect illness causing longer sleep, rather than the other way round. These studies show associations, not proof of cause.

Does everyone need the same amount?

No. Sleep need varies from person to person, and it changes across life.

• Differences in vulnerability. A 2004 study in Sleep found that people differ consistently in how much sleep loss affects them. Some are hit hard by a short night; others hold up better. These differences were stable, almost like a trait.
• Genuine short sleepers are rare. A 2009 study in Science described a gene variant in a family whose members naturally slept only about six hours and felt fine. Variants like this are very rare. Most people who believe they need little sleep are simply used to being tired.
• Age. Teenagers need more sleep than adults, and older adults often sleep less deeply, though their need does not drop as much as many assume.

What is sleep debt, and can you pay it back?

Sleep debt is the gap between the sleep you need and the sleep you get, added up over days. If you need 8 hours and sleep 6.5 every weeknight, you build up about 7.5 hours of debt in a working week.

Paying it back is harder than it sounds:

• In a 2003 study in the Journal of Sleep Research, people whose sleep had been heavily restricted for a week did not fully return to their starting performance after three nights of recovery sleep.
• In a 2019 study in Current Biology, sleeping in at the weekend did not prevent the drop in insulin sensitivity caused by short weeknight sleep.

Recovery sleep does help with sleepiness, so it is worth doing. But the most reliable way to avoid sleep debt is to get enough sleep on most nights.

How can you find your own sleep need?

There is no blood test for sleep need, but you can estimate it.

1. Try the holiday test. During a stretch of free days with no alarm, note when you naturally fall asleep and wake. The first few nights are usually long as you pay back debt. After that, your sleep tends to settle near your real need.
2. Watch your daytime signals. If you need an alarm every day, fall asleep within minutes of lying down, or feel heavy in the mid-afternoon, you may be running short.
3. Experiment for two weeks. Move your bedtime 15 to 30 minutes earlier while keeping the same wake time, and notice how you feel.

Apps can help you see the pattern. Somnia Pro, for example, estimates your sleep need and sleep debt from your logged nights. Treat any such number as an estimate, not a measurement, and trust how you feel during the day as well.

When is it worth talking to a doctor?

If you regularly sleep 7 to 9 hours and still feel unrefreshed, or you are often sleepy during the day, something other than sleep length may be going on. Loud snoring, gasping or pauses in breathing can point to sleep apnea. Trouble falling or staying asleep at least three nights a week for three months or more may be chronic insomnia. For chronic insomnia, the American College of Physicians recommends cognitive behavioral therapy for insomnia (CBT-I) as the first treatment. A clinician can help you find the right one.

This article is for general information and is not medical advice. If you have ongoing sleep problems, talk with a qualified clinician.