# Sleep duration & health: what the research actually says

How much sleep adults actually need, what happens below seven hours, and why you stop noticing the impairment long before it stops happening.



## All studies

- **Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society** — Watson NF, Badr MS, Belenky G, et al. (2015), Sleep 38(6):843–844. Adults should sleep ≥7 h per night on a regular basis; <7 h is associated with weight gain, diabetes, hypertension, depression and mortality.

- **National Sleep Foundation's sleep time duration recommendations: methodology and results summary** — Hirshkowitz M, Whiton K, Albert SM, et al. (2015), Sleep Health 1(1):40–43. 7–9 h recommended for adults 26–64; 7–8 h for 65+.

- **Trends in self-reported sleep duration among US adults from 1985 to 2012** — Ford ES, Cunningham TJ, Croft JB (2015), Sleep 38(5):829–832. Population sleep has shortened; the share of adults sleeping ≤6 h rose to ~29%.

- **The effects of sleep extension on the athletic performance of collegiate basketball players** — Mah CD, Mah KE, Kezirian EJ, Dement WC (2011), Sleep 34(7):943–950. Extending sleep to ~10 h improved sprint time, shooting accuracy, reaction time and mood.

- **Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies** — Cappuccio FP, D'Elia L, Strazzullo P, Miller MA (2010), Sleep 33(5):585–592. Both short (<7 h) and long (>8–9 h) habitual sleep are associated with higher mortality — a U-shaped curve.

- **The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation** — Van Dongen HP, Maislin G, Mullington JM, Dinges DF (2003), Sleep 26(2):117–126. Two weeks at 6 h/night produced deficits equal to two nights of total deprivation — while subjects felt only mildly sleepy. You adapt to feeling tired, not to being impaired.

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Educational summary of published research, not medical advice. Screening scores are not diagnoses. If a score is elevated or you feel unwell, talk to a clinician.

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