The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults 18 to 60 sleep at least seven hours a night, a conclusion a 15-person expert panel reached after a year reviewing more than 5,000 studies. But a number alone doesn't tell the whole story: large population studies that track sleep for years also find that sleeping unusually little — or unusually long — comes with a higher risk of death during follow-up, and newer research suggests how consistently you sleep may matter as much as how many hours you log.
| Sleep pattern (vs. a reference/average-duration group) | Risk of death during follow-up |
|---|---|
| Habitually short sleep | About 12% higher |
| Average duration | Reference group |
| Habitually long sleep | About 30% higher |
These figures come from a meta-analysis pooling more than 1.3 million adults across 16 studies.¹ The exact number of hours that counted as "short" or "long" varied by study, which is why the table reports relative risk rather than a single cutoff — more on that below.
How many hours is actually "enough"?
The seven-hours-or-more figure comes from a formal consensus process, not a single study: the AASM and Sleep Research Society convened 15 sleep specialists, who used a structured voting method to review the existing evidence and reach agreement. Their conclusion was that adults 18 to 60 should regularly get seven or more hours to support health and reduce the risk of problems linked to insufficient sleep — including weight gain, diabetes, high blood pressure, depression, and accidents. Six hours or less, on a regular basis, was the panel's line for inadequate sleep in most adults.
Is sleeping too much also something to worry about?
The same meta-analysis that found short sleep carries more risk also found long sleep carries more — in fact, a larger relative increase (about 30% versus about 12%). That's worth taking seriously, but also worth reading carefully: these are observational studies, meaning they tracked who slept how much and who later died, not controlled experiments. People who are already managing a serious illness commonly sleep more than average, for reasons that have nothing to do with the extra hours themselves — so some, though not necessarily all, of the long-sleep finding likely reflects underlying health problems rather than long sleep causing harm on its own. The expert consensus panel set no firm upper limit for this reason: sleeping more than nine hours may be entirely appropriate for some people, including those catching up on sleep debt, and may or may not signal something worth a closer look in others.
Does consistency matter more than the total?
A 2024 analysis of UK Biobank data suggests it might. Researchers tracked nearly 61,000 adults (average age 63) using wrist accelerometers for about a week each, calculated a sleep regularity score for each person, and then followed the group for up to almost eight years. People with the most regular sleep-wake timing had a 20% to 48% lower risk of dying from any cause than those with the least regular sleep, after adjusting for age, sex, and a range of lifestyle and health factors.² When the researchers compared regularity and duration head-to-head in the same statistical models, regularity came out as the stronger predictor of the two.
That's a striking result, with real limits attached. The study is observational, like the others here, so it shows an association, not proof that tightening your schedule by itself extends life. The UK Biobank is also known to skew healthier than the general population — people who volunteer to wear a tracker for a week tend to be more health-conscious to begin with — and the average participant was in their early 60s, so the finding hasn't been separately established in younger adults.
What if seven consistent hours isn't realistic right now?
Shift work, new parenthood, and caregiving all make a fixed seven-hour block hard to guarantee, and none of the research above expects perfection. The regularity finding points to a more flexible lever: the timing of sleep, not just its length, appears to carry independent weight. Anchoring a wake-up time you can hit most days — even when the bedtime slips — is often more achievable than forcing an early bedtime every single night, and it's the piece the newer evidence suggests may matter most.
What the research says
Cappuccio and colleagues pooled 16 prospective studies covering more than 1.3 million adults and 112,566 deaths and found that both short sleep (relative risk 1.12) and long sleep (relative risk 1.30) were associated with a higher risk of death than a middle, reference duration.¹ The studies defined "short" and "long" differently from one another, the data relied on self-reported sleep rather than objective measurement, and — as with any observational pooling — the analysis can show association but can't rule out that illness is driving some of the long-sleep result rather than the reverse.
Windred and colleagues followed 60,977 UK Biobank participants for up to 7.8 years using objectively measured sleep regularity and found it predicted all-cause, cancer, and cardiometabolic mortality more strongly than sleep duration did in the same models.² The cohort's healthy-volunteer skew and older average age (62.8 years) are real limits on how far the finding generalizes, and — again — an observational design means the result shows a strong association, not a demonstrated cause.
The AASM/Sleep Research Society panel's seven-or-more-hours recommendation is a consensus statement synthesizing that broader evidence base through a structured expert process, not a single trial of its own — its strength is the breadth of literature it reviewed, and its explicit position is that no single number works for everyone, particularly above nine hours.³
What you can do this week
- Pick a wake time you can hit most days, and protect it first. The regularity research above suggests consistency may matter as much as total hours — a fixed wake time is usually easier to control than an early bedtime.
- Treat six hours or less as a flag worth noticing, not a badge. That's the threshold the AASM/Sleep Research Society panel called inadequate for most adults, even for people who feel fine running on it.
- If weight gain is one of the things short sleep has left you managing, Pallas prescribes compounded semaglutide and tirzepatide when a US-licensed clinician decides it's appropriate.
