How Much Sleep Do You Actually Need?

The short answer: most adults need seven to nine hours of sleep a night. The American Academy of Sleep Medicine and Sleep Research Society recommend seven or more hours for adults aged 18 to 60, setting no upper limit. The National Sleep Foundation puts the range at seven to nine hours, and seven to eight for adults over 65.

Sleep need is the amount of sleep a person requires for normal daytime alertness and long-term health — which is not the same thing as habitual sleep duration, the amount they actually get.

The headline numbers

• 7 or more hours per night — the recommendation for adults aged 18 to 60 from a 15-member panel convened by the American Academy of Sleep Medicine and the Sleep Research Society (Watson and colleagues, Sleep, 2015).
• 6 or fewer hours is inadequate — the same panel judged six or fewer hours insufficient to sustain health and safety in adults (American Academy of Sleep Medicine, 2015).
• 7 to 9 hours for adults, 7 to 8 from age 65 — age-banded recommendations from an 18-member National Sleep Foundation panel drawn from 12 stakeholder organisations (Hirshkowitz and colleagues, Sleep Health, 2015).
• Relative risk of death 1.12 (95% CI 1.06 to 1.18) for short sleep, 1.30 (95% CI 1.22 to 1.38) for long sleep — pooled from 27 cohort samples, 1,382,999 people and 112,566 deaths (Cappuccio and colleagues, Sleep, 2010).
• Around 7 hours sits at the bottom of the risk curve — all-cause mortality rose by a relative risk of 1.06 (95% CI 1.04 to 1.07) per hour below seven and 1.13 (95% CI 1.11 to 1.15) per hour above (Yin and colleagues, Journal of the American Heart Association, 2017).
• Roughly a third of US adults fall short — 65.2% of 444,306 adults surveyed reported at least seven hours (Liu and colleagues, MMWR, 2016, using 2014 surveillance data).

How much sleep is recommended at each age?

Two expert panels published age-banded guidance in 2015 and agree closely. The National Sleep Foundation covers the whole lifespan; the AASM and Sleep Research Society addressed adults aged 18 to 60 and declined to set an upper limit.

Age group	Recommended sleep per 24 hours	Issuing body
Newborns (0 to 3 months)	14 to 17 hours	National Sleep Foundation (2015)
Infants (4 to 11 months)	12 to 15 hours	National Sleep Foundation (2015)
Toddlers (1 to 2 years)	11 to 14 hours	National Sleep Foundation (2015)
Preschoolers (3 to 5 years)	10 to 13 hours	National Sleep Foundation (2015)
School-age children (6 to 13 years)	9 to 11 hours	National Sleep Foundation (2015)
Teenagers (14 to 17 years)	8 to 10 hours	National Sleep Foundation (2015)
Adults (18 to 64 years)	7 to 9 hours	National Sleep Foundation (2015)
Adults (18 to 60 years)	7 or more hours, no upper limit set	AASM and Sleep Research Society consensus (2015)
Older adults (65 years and over)	7 to 8 hours	National Sleep Foundation (2015)

Why is the answer a range instead of a number?

Both 2015 panels used a structured voting procedure, the RAND/UCLA Appropriateness Method, rather than a single experiment: experts rated candidate durations against the evidence and voted until they converged. A range is the honest output, because sleep need genuinely varies between individuals and no trial has randomised people to different durations for decades and counted the outcomes.

The National Sleep Foundation panel added its own caveat: durations outside the range may suit some people, but deviating far from it is rare and can signal an underlying health problem (Hirshkowitz and colleagues, Sleep Health, 2015).

Is 6 hours of sleep ever enough?

For almost everyone, no. The key experiment randomised 48 healthy adults aged 21 to 38 to 4, 6 or 8 hours of time in bed for 14 consecutive nights under continuous laboratory monitoring (Van Dongen and colleagues, Sleep, 2003).

Restriction to 4 or 6 hours produced significant cumulative, dose-dependent deficits on every cognitive task measured. Chronic restriction to six hours or less produced performance deficits equivalent to as much as two nights of total sleep deprivation.

The finding that matters most for self-assessment: subjective sleepiness ratings spiked early, then barely moved, and did not reliably separate the 6-hour group from the 4-hour group. Participants were largely unaware of how impaired they had become — which is why feeling fine on six hours is weak evidence that six hours is enough. The study was small and short, though: 48 young healthy volunteers over 14 nights, with time in bed controlled rather than sleep obtained.

Are natural short sleepers real, and could you be one?

They are real, and they are rare. The clearest evidence is a mutation in the gene DEC2 (hDEC2-P385R) found in a mother and daughter who habitually slept an average of 6.25 hours a night, against 8.06 hours for non-carrier relatives in the same family (He and colleagues, Science, 2009).

Two details keep this in proportion. The variant was absent from over 250 control DNA samples screened in that study, and mice engineered to carry it slept measurably less than controls — so the effect is genuine, but the human evidence rests on one rare variant in a single family.

None of that supports assuming you are a natural short sleeper because you get by on six hours. Chronic restriction with a blunted sense of impairment is far commoner.

Do older adults need less sleep?

Sleep changes with age far more than sleep need does. A meta-analysis of 65 studies covering 3,577 healthy people aged 5 to 102 found that in adults, total sleep time, sleep efficiency and the percentages of slow-wave and REM sleep all declined with age, while sleep latency, light sleep and time awake after sleep onset rose — though only sleep efficiency kept declining significantly after age 60 (Ohayon and colleagues, Sleep, 2004).

Capacity does shift. Given extended sleep opportunities — 12 hours at night plus 4 in the afternoon for 3 to 7 days — 18 older healthy adults settled at 7.4 hours of daily sleep (SEM 0.4) against 8.9 hours (SEM 0.4) in 35 younger ones (Klerman and Dijk, Current Biology, 2008).

Note where that older-adult figure lands: 7.4 hours is still above the seven-hour floor. The recommended minimum from age 65 drops only to seven to eight hours, and never falls below seven at any adult age. Fragmented, shallower sleep in later life is a change in architecture, not permission to sleep five hours.

How can you tell whether you are getting enough?

Daytime function is the practical test, not a score in an app: waking without dragging yourself out of bed, staying alert through the afternoon without unplanned dozing, and not needing hours of extra weekend sleep to feel normal.

Consumer trackers are useful for spotting patterns and unreliable as verdicts. When seven consumer sleep-tracking devices were tested against polysomnography across three nights in 34 healthy young adults, epoch-by-epoch sensitivity for detecting sleep was high (all at or above 0.93), but specificity for detecting wake was low to medium (0.18 to 0.54), sleep stage estimates were inconsistent, and performance worsened on disrupted nights (Chinoy and colleagues, Sleep, 2021). Sleep clinicians have also described orthosomnia, a pattern in which patients chase perfect tracker data in ways that can worsen the problem (Baron and colleagues, Journal of Clinical Sleep Medicine, 2017).

Duration is not the whole of sleep health either. The 2015 consensus panel was explicit that the benefits require appropriate timing, daily regularity, good quality and the absence of sleep disorders — not just hours logged.

Persistently unrefreshing sleep despite adequate time in bed, loud snoring, witnessed pauses in breathing or heavy daytime sleepiness all warrant assessment by a doctor rather than another week of tracker data. Obstructive sleep apnoea is common, treatable, and invisible to duration alone.

Why does sleeping too long look risky as well?

The epidemiology of sleep duration is U-shaped, and the long-sleep arm is the more suspicious half. A meta-analysis pooling 137 prospective cohorts and 5,134,036 participants found long sleep associated with mortality at a risk ratio of 1.39 (95% CI 1.31 to 1.47), stroke at 1.46 (95% CI 1.26 to 1.69) and cardiovascular disease at 1.25 (95% CI 1.14 to 1.37) — while calling for future work to establish whether the relationship is causal at all (Jike and colleagues, Sleep Medicine Reviews, 2018).

A pooled cohort of 322,721 adults across Japan, China, Singapore and Korea put the lowest risk at seven hours in both sexes, with the strongest association at ten hours or more: hazard ratio 1.34 (95% CI 1.26 to 1.44) in men, 1.48 (95% CI 1.36 to 1.61) in women (Svensson and colleagues, JAMA Network Open, 2021).

The likeliest explanation is not that extra sleep is harmful. As the moderator of the 2015 consensus panel put it on publication, long sleep duration is more likely to reflect chronic illness than to cause it, and few experimental studies have tested long sleep directly. The panel therefore set no upper limit, noting that more than nine hours may be appropriate for young adults, people recovering from sleep debt, and people who are ill.

What this evidence does not establish

• A personal number. No published method identifies an individual’s exact sleep requirement. The guidelines define a range for healthy people, not a target for one person.
• That long sleep causes harm. The association is large and consistent; the causal claim is not established, and reverse causation is the leading explanation.
• That sleeping more improves outcomes. No long-term randomised trial has assigned adults to different sleep durations and measured disease or death.
• That the adult recommendation covers everyone. The 2015 consensus panel addressed healthy adults aged 18 to 60, and does not speak to pregnancy, shift work, illness or people over 60. Nor is there a validated test for the rare natural short sleeper trait.

Limitations of the sleep duration evidence

• Almost all of it uses self-reported sleep. In 669 middle-aged adults measured by wrist actigraphy, average measured sleep was 6.0 hours against 6.8 hours self-reported, the correlation was 0.47, and people sleeping five hours over-reported by about 1.2 hours (Lauderdale and colleagues, Epidemiology, 2008). Every questionnaire-based risk curve inherits that bias.
• Reverse causation on the long-sleep arm. Cancer, heart failure, depression, infection and the drugs used to treat them all lengthen sleep. A cohort measuring sleep once at baseline cannot separate long sleep as cause from long sleep as symptom.
• Confounding by illness and circumstance. Short sleep clusters with shift work, poverty, pain and untreated sleep apnoea. Adjustment reduces this but cannot remove what was never measured.
• Heterogeneity and inconsistent definitions. The 2010 meta-analysis reported significant heterogeneity for both short sleep (P = 0.02) and long sleep (P less than 0.0001), and cohorts cut short and long sleep at different thresholds, which alone can move a pooled estimate.
• Consensus statements are votes, not experiments. Both 2015 documents are structured expert judgements about largely observational evidence, and both say so.

Funding and declared interests

The 2015 adult consensus project was funded by the American Academy of Sleep Medicine and the Sleep Research Society, and by the National Healthy Sleep Awareness Project, their partnership with the US Centers for Disease Control and Prevention. The lifespan recommendations came from a panel convened by the National Sleep Foundation, a non-profit advocacy organisation. Both bodies have an institutional interest in the salience of sleep, worth naming even though their conclusions align with the wider literature. The 2021 device study was funded by the US Office of Naval Research, with no reported financial conflicts and no involvement from the device companies tested.

The bottom line

Seven to nine hours is the answer for the large majority of adults, with seven the floor two independent expert panels converged on. Below it, the experimental evidence for accumulating impairment is strong and the person affected is usually the last to notice. Above nine, the risk signal is probably illness showing up in the sleep record rather than sleep harming health.

The practical move: allow the opportunity for seven to nine hours on a regular schedule, then judge by how the following day goes rather than by a percentage on a wrist device.

This article is educational and is not medical advice. It summarises published research and is not a substitute for assessment by a qualified clinician, who can evaluate symptoms such as persistent unrefreshing sleep, snoring or daytime sleepiness that this kind of general guidance cannot.

References

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