How much sleep do adults need? What the research and guidelines say

Eight hours is the number most people carry around as the right amount of sleep. Sleep experts are less precise and more generous: the main recommendations for adults give a range of seven to nine hours, with seven as the floor.

Those figures come from expert panels that reviewed the research on sleep and health, not from a single study. The research behind them links regularly sleeping less than seven hours to a long list of health problems, and also finds that very long sleep goes with higher risk, though often for different reasons.

What sleep experts recommend for adults

In 2015, the American Academy of Sleep Medicine and the Sleep Research Society published a joint consensus in the journal SLEEP. Its central recommendation: adults should sleep 7 or more hours per night on a regular basis to promote optimal health. The panel noted that healthy sleep also requires good quality, appropriate timing and regularity, and the absence of sleep disorders.

The National Sleep Foundation convened its own expert panel the same year and gave ranges by age. It judged 7 to 9 hours for young adults and adults, and 7 to 8 hours of sleep for older adults. MedlinePlus uses similar figures, giving adults 7 to 9 hours a day and teenagers 8 to 10.

What the research links to short sleep

The consensus statement summarizes what the evidence connects to sleeping too little. Sleeping less than 7 hours per night on a regular basis is associated with adverse health outcomes, including weight gain and obesity, diabetes, hypertension, heart disease and stroke, depression, and increased risk of death.

Short sleep also affects daily life. The same statement links it to impaired immune function, more pain, worse performance, more errors and a greater risk of accidents. MedlinePlus adds that when you don’t get enough sleep (sleep deprivation), it does more than just make you feel tired, affecting mood as well as physical health.

Is sleeping too long also a problem?

The largest pooled analysis of sleep and death combined 16 studies with 27 separate groups and nearly 1.4 million participants, followed for up to 25 years. Short duration of sleep was associated with a greater risk of death, about 12% higher, compared with people sleeping a typical amount.

Long sleep went with about 30% higher risk. That does not necessarily mean too much sleep is harmful. People who are unwell, depressed or have undiagnosed conditions often sleep longer, so long sleep can be a symptom rather than a cause. The consensus statement reflects this: sleeping more than 9 hours may be appropriate for young adults, people recovering from sleep debt and people who are ill, and for others it is uncertain whether sleeping more than 9 hours per night is associated with health risk.

Do sleep needs change with age?

Children and teenagers need more sleep than adults, and needs fall through childhood. After that, the picture is steadier than many people think. MedlinePlus notes that some people think adults need less sleep as they age, but there is no evidence to support this.

What changes is how well older adults sleep. They often get less sleep or spend less time in the deepest stages, which is why the National Sleep Foundation range for older adults is slightly narrower. Its panel also stressed that sufficient sleep duration requirements vary across the lifespan and from person to person.

Why sleep quality and timing matter as well as hours

Hours are only part of the picture. MedlinePlus points out that it’s not just the number of hours of sleep you get that matters: sleep that is broken, shallow or badly timed can leave people tired even after a long night. That is one reason expert panels frame their advice around healthy sleep in general, not duration alone.

Timing shifts with age too. Teenagers tend to fall asleep later and wake up later, which can conflict with the early school start times, according to MedlinePlus, so many get well under the 8 to 10 hours recommended for them even when they spend enough time in bed on weekends.

What the sleep duration research cannot tell us

Most studies relied on people’s own estimates of how long they sleep, which are often off by an hour or more. They also cannot fully separate the effects of sleep from the health problems that change sleep, especially for long sleepers.

The recommendations are consensus judgments by expert panels, built on observational evidence and short experiments, not on long trials that assigned people to sleep more or less. They describe healthy adults without sleep disorders, and they cannot say exactly how much sleep any one person needs.

What the sleep evidence adds up to

For most adults, the evidence and the expert panels point to at least seven hours a night, with seven to nine as a common range and eight hours comfortably inside it. Regularly sleeping less than that is linked to many health problems.

Sleeping far outside the usual range, whether much shorter or much longer, is unusual. The National Sleep Foundation notes that people who habitually sleep outside the normal range may be showing signs of health problems, and the consensus statement recommends that people concerned they are sleeping too little or too much should consult their healthcare provider.