How Much Sleep Do Adults Need?

Adults need 7 hours of sleep or more a night, regularly. That’s the joint recommendation of the American Academy of Sleep Medicine (AASM) and the Sleep Research Society, and the National Sleep Foundation recommends 7 to 9 hours for adults aged 18 to 64, and 7 to 8 for those 65 and over. These are hours actually asleep, not hours in bed.

This article is general information, not medical advice.

The Recommendations

• AASM and Sleep Research Society (Watson and colleagues, 2015): adults should sleep 7 or more hours a night on a regular basis. Sleeping less is linked to weight gain and obesity, diabetes, high blood pressure, heart disease and stroke, depression, impaired immune function, more pain, worse performance, more errors, and a greater risk of accidents. Sleeping more than 9 hours may be appropriate for young adults, people recovering from sleep debt, and people who are ill.
• National Sleep Foundation (Hirshkowitz and colleagues, 2015): 7 to 9 hours for adults aged 18 to 64, with 6 or 10 hours “may be appropriate”; 7 to 8 hours for adults 65 and over, with 5 to 6 or 9 “may be appropriate”.

Short and Long Sleep

In a meta-analysis of 16 studies with 1.4 million people, Cappuccio and colleagues found that short sleepers, usually under 5 to 7 hours, had a 12% higher risk of dying during follow-up, and long sleepers, usually over 8 to 9 hours, a 30% higher risk. Long sleep is likely to be partly a sign of existing illness rather than its cause, and these studies relied on people reporting their own sleep, so the long-sleep finding is the less certain of the two.

Time Asleep Versus Time in Bed

Lying in bed for 8 hours doesn’t mean 8 hours of sleep. Falling asleep takes time, and most people wake briefly during the night. The share of time in bed actually asleep is your sleep efficiency; see What Makes a Good Night’s Sleep? If you need 7 hours of sleep and usually sleep 85% of the time you’re in bed, you need a little over 8 hours in bed.

Judging Your Own Sleep

• How you feel during the day is a good check: if you need an alarm every day and catch up at weekends, you’re probably short.
• Look at weekly averages, since one short night matters less than a pattern.
• Keep regular times. Going to bed and waking at consistent times matters as well as length; see What Is Sleep Regularity?

If you often sleep poorly despite enough time in bed, or snore loudly and feel unrefreshed, talk to a doctor; insomnia and sleep apnea are common and treatable.

Following It in Kaizora

From your watch’s or ring’s sleep data, Kaizora derives each sleep’s Total Sleep Time, every stage of sleep together, as the AASM defines it, using the one recording with the most of that sleep so two trackers’ copies of a night count once. Time Asleep holds sleep with no stages recorded, and Time in Bed your time in bed. The AASM’s 7 hours comes as a default reference range on Total Sleep Time, judged on the average of the 7 days ending each day, naps included, so one short night in a good week isn’t flagged. The Kaizora Sleep Score’s duration component scores best from 7 to 9 hours.

The Short Version

• Adults need 7 hours of sleep or more, regularly; 7 to 9 is the National Sleep Foundation’s range.
• Short sleep is linked to many health problems; very long sleep is often a sign of illness.
• Count hours asleep, not hours in bed.

Sources

• Watson NF et al., “Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society,” Journal of Clinical Sleep Medicine 11, no. 6 (2015): 591–592. doi:10.5664/jcsm.4758
• Hirshkowitz M et al., “National Sleep Foundation’s sleep time duration recommendations: methodology and results summary,” Sleep Health 1, no. 1 (2015): 40–43. doi:10.1016/j.sleh.2014.12.010
• Cappuccio FP et al., “Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies,” Sleep 33, no. 5 (2010): 585–592. doi:10.1093/sleep/33.5.585