GradedHealth

How much sleep do you need, and does a regular bedtime matter?

Most adults are advised to sleep 7 to 9 hours. Large studies link a steady bedtime and wake time to longer life, though not proof of cause.

Published October 2026

Short answer

Adults are advised to sleep 7 to 9 hours. Large studies link very short or long sleep, and irregular bedtimes, to higher death risk, but they cannot show cause. Evidence grade B (Moderate). Large meta-analyses and UK cohorts of observational data; capped at B because no trial has tested sleep timing on death, with no further downgrade for the main answer.

Key takeaways

  • Expert panels advise 7 to 9 hours a night for adults and 7 to 8 hours for older adults [1].
  • In a 2025 meta-analysis of 79 cohort studies, sleeping under 7 hours was linked to 14% higher death risk, and 9 hours or more to 34% higher, compared with 7 to 8 hours [2].
  • In a UK cohort of about 61,000 people, the most regular sleepers had 20% to 48% lower all-cause mortality than the least regular [3].
  • These are observational links, and the authors of the long-sleep review say whether the link is causal still needs testing [4].
  • Weekend catch-up sleep gives mixed results: a large UK cohort found no link to death or heart disease [5].

The short version

How much sleep do you need? The expert panel that reviewed the evidence advises 7 to 9 hours a night for adults, and 7 to 8 hours for older adults [1]. Large studies link sleeping much less or much more than this to a higher risk of early death, and a steady bedtime and wake time also appears to matter [2][3]. Most of this evidence is observational, so it shows links, not proof of cause.

What the studies show

How many hours

A 2017 meta-analysis of cohort studies found the lowest death risk at about 7 hours a night. Each hour below 7 was linked to a 6% higher risk, and each hour above 7 to a 13% higher risk [6]. A 2025 meta-analysis of 79 cohorts put the figures at 14% higher risk for under 7 hours and 34% for 9 hours or more, compared with 7 to 8 hours [2]. An umbrella review of 69 meta-analyses linked inappropriate sleep durations to cardiovascular disease, cognitive decline, depression, falls, frailty and stroke [7].

Bedtime and a steady schedule

The studies do not identify a best clock time, because most reported linear associations rather than thresholds [8]. What they point to is a consistent schedule. A 2020 systematic review of 41 studies (92,340 people) found that later sleep timing and greater day-to-day variability were generally linked to worse health, and that consistent bedtimes and wake times were linked to better health [8]. In a UK cohort of about 61,000 people who wore accelerometers, the most regular sleepers had 20% to 48% lower all-cause mortality than the least regular, and regularity predicted death risk better than sleep duration did [3]. A 2025 systematic review of 59 studies found moderate-certainty evidence that irregular sleep timing is linked to depression, anxiety, higher body mass index, insulin resistance, hypertension and cardiovascular events [9].

Weekends and catch-up sleep

Catch-up sleep means sleeping longer at weekends. In a UK accelerometer cohort of 73,513 adults followed for about 8 years, catching up by 2 hours or more was not linked to death (hazard ratio 1.17, 95% CI 0.97 to 1.41) or to heart disease [5]. The authors note that this does not match earlier recommendations [5]. Other UK cohorts found benefits only in some groups. Among people who slept little on weekdays, catching up more than 1.5 hours was linked to lower type 2 diabetes risk [10]. A catch-up of 1 to 1.5 hours was linked to lower dementia risk [11]. A 2020 review reported that catch-up sleep was linked to better health [8]. The 2023 National Sleep Foundation panel judged that weekend catch-up may be beneficial when weekday sleep is short [12].

Early and late types

A 37-year Finnish study of 23,854 adults found a 9% higher death rate for evening types in its adjusted model, but the authors say the difference was mostly due to smoking and alcohol [13]. Social jet lag is the gap between sleep timing on workdays and on free days. It was linked to higher body mass index and fat mass in 43 studies of 231,648 people, but these were correlational studies and the authors call for tests of causality [14]. In 25 observational studies, the link between social jet lag and depressive symptoms was tiny, explaining 0.24% of the variation [15].

Older adults

The 7 to 8 hour guidance for older adults comes from the same expert panel [1]. A 2025 review of 17 studies found that both 5 and 9 hours of sleep were associated with frailty, but 13 of the 17 studies were cross-sectional [16]. For thinking and memory, a 2026 umbrella review of 13 reviews found a U-shaped link between sleep duration and cognitive decline, but most of the evidence was rated low certainty [17].

The nuances

Most of these links are observational. People who sleep much less or much more than average may differ in other ways, and the review of long sleep says that whether the link is causal still needs testing [4]. In the 2025 mortality meta-analysis, the risk from long sleep was higher in women than in men [2].

Trials of sleep extension are few and small. In an 80-person trial of adults with overweight who usually slept under 6.5 hours, extending sleep by about 1.2 hours a night reduced energy intake by 270 kcal a day compared with the control group [18]. A review of seven sleep-extension studies (138 people) found preliminary improvements in insulin sensitivity [19]. No trial we read tests whether a steadier schedule lowers death risk, and the authors of the regularity review call for such trials [9].

What this means for you

The evidence points to a practical target rather than one perfect bedtime. Most adults can aim for 7 to 9 hours [1], and keep bed and wake times fairly steady, which the 2023 panel called important for health and performance [12]. If you usually sleep under 7 hours, or wake unrested most days, talk to a doctor. For light and the body clock, see the Morning Light page. For side effects and safety notes, see the Sleep page.

Go deeper

  • Sleep — Expert panels advise 7 to 9 hours of sleep a night for adults.
  • Morning Light — Bright light, often taken in the morning and usually from a light box, helps lift depression and improve sleep in meta-analyses of clinical trials, and more da…

References

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  2. Imbalanced sleep increases mortality risk by 14-34%: a meta-analysis.. Geroscience, 2025.
  3. Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study.. Sleep, 2024.
  4. Long sleep duration and health outcomes: A systematic review, meta-analysis and meta-regression.. Sleep Med Rev, 2018.
  5. Device-measured weekend catch-up sleep, mortality, and cardiovascular disease incidence in adults.. Sleep, 2024.
  6. Relationship of Sleep Duration With All-Cause Mortality and Cardiovascular Events: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies.. J Am Heart Assoc, 2017.
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  8. Sleep timing, sleep consistency, and health in adults: a systematic review.. Appl Physiol Nutr Metab, 2020.
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  10. Associations of accelerometer-measured weekend sleep catch-up and loss with risk of type 2 diabetes: a prospective cohort study.. Diabetes Res Clin Pract, 2025.
  11. Accelerometer-measured weekend catch-up sleep and incident dementia: A prospective cohort study.. Alzheimers Dement, 2025.
  12. The importance of sleep regularity: a consensus statement of the National Sleep Foundation sleep timing and variability panel.. Sleep Health, 2023.
  13. Chronotype and mortality - a 37-year follow-up study in Finnish adults.. Chronobiol Int, 2023.
  14. Social jetlag and obesity: A systematic review and meta-analysis.. Obes Rev, 2024.
  15. Social jet lag and mental health outcomes: A systematic review and meta-analysis.. Acta Psychol (Amst), 2025.
  16. Sleep quality and duration and frailty in older adults: a systematic review.. Front Public Health, 2025.
  17. Duration and Quality of Sleep as Risk Factors for Cognitive Impairment: An Umbrella Review of Systematic Reviews.. Int J Geriatr Psychiatry, 2026.
  18. Effect of Sleep Extension on Objectively Assessed Energy Intake Among Adults With Overweight in Real-life Settings: A Randomized Clinical Trial.. JAMA Intern Med, 2022.
  19. The effects of sleep extension on cardiometabolic risk factors: A systematic review.. J Sleep Res, 2019.