Sleep duration and regularity

Practical note

Graded low: the ranges come from expert consensus (RAND/UCLA Appropriateness Method) built on mainly observational evidence, not from trials that assigned sleep durations; the separate AASM/SRS consensus (2015) was not quoted because its full text could not be fetched.

Safety note

The ranges are for healthy people without a sleep disorder; the panel noted that habitual sleep far outside the range can be a sign of a health problem.

Sources

• Supports“For teenagers, 8 to 10 hours was considered appropriate, 7 to 9 hours for young adults and adults, and 7 to 8 hours of sleep for older adults.” (Abstract, Results) Hirshkowitz M, Whiton K, Albert SM, Alessi C, Bruni O, DonCarlos L, Hazen N, Herman J, Katz ES, Kheirandish-Gozal L, Neubauer DN, O'Donnell AE, Ohayon M, Peever J, Rawding R, Sachdeva RC, Setters B, Vitiello MV, Ware JC, Adams Hillard PJ. 2015. Sleep Health. National Sleep Foundation's sleep time duration recommendations: methodology and results summary. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Supports“Individuals vary in their sleep needs, but most adults require between 7 and 9 hours a night to feel properly refreshed and function at their best the next day.” (Adult Sleep) Sleep Health Foundation. 2024. Sleep Health Foundation (Australia). How much sleep do you really need? Sleep Health Foundation, all rights reserved; short attributed quotes only; credit Sleep Health Foundation
• Context“Sufficient sleep duration requirements vary across the lifespan and from person to person.” (Abstract, Conclusions) Hirshkowitz M, Whiton K, Albert SM, Alessi C, Bruni O, DonCarlos L, Hazen N, Herman J, Katz ES, Kheirandish-Gozal L, Neubauer DN, O'Donnell AE, Ohayon M, Peever J, Rawding R, Sachdeva RC, Setters B, Vitiello MV, Ware JC, Adams Hillard PJ. 2015. Sleep Health. National Sleep Foundation's sleep time duration recommendations: methodology and results summary. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine

Practical note

Graded low: observational cohorts with self-reported sleep; not upgraded because of significant heterogeneity and possible reverse causation for long sleep. The 2010 meta-analysis pooled 16 studies with 1.38 million participants (short sleep RR 1.12, long sleep RR 1.30).

Safety note

Long sleep may partly reflect existing illness rather than cause harm, so this association does not show that sleeping less lowers risk.

Sources

• Supports“Both short and long duration of sleep are significant predictors of death in prospective population studies.” (Abstract, Conclusion) Cappuccio FP, D'Elia L, Strazzullo P, Miller MA. 2010. Sleep. Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Context“Abnormally short and long sleep are associated with premature mortality, and achieving optimal sleep duration has been the focus of sleep health guidelines.” (Abstract) Windred DP, Burns AC, Lane JM, Saxena R, Rutter MK, Cain SW, Phillips AJK. 2024. Sleep. Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study. CC BY (per Europe PMC); credit Windred et al., Sleep 2024; Courtesy of the U.S. National Library of Medicine

Practical note

Graded low: observational evidence; the obesity meta-analysis was mostly cross-sectional and its authors noted that causal inference is difficult; the diabetes meta-analysis (10 prospective studies, 107,756 participants) defined short sleep as 5-6 hours or less a night and showed heterogeneity.

Safety note

Long habitual sleep was also associated with a higher type 2 diabetes risk in the same meta-analysis.

Sources

• Supports“Cross-sectional studies from around the world show a consistent increased risk of obesity amongst short sleepers in children and adults.” (Abstract, Conclusions) Cappuccio FP, Taggart FM, Kandala NB, Currie A, Peile E, Stranges S, Miller MA. 2008. Sleep. Meta-analysis of short sleep duration and obesity in children and adults. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Supports“Quantity and quality of sleep consistently and significantly predict the risk of the development of type 2 diabetes.” (Abstract, Conclusions) Cappuccio FP, D'Elia L, Strazzullo P, Miller MA. 2010. Diabetes Care. Quantity and quality of sleep and incidence of type 2 diabetes: a systematic review and meta-analysis. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Context“Causal inference is difficult due to lack of control for important confounders and inconsistent evidence of temporal sequence in prospective studies.” (Abstract, Conclusions) Cappuccio FP, Taggart FM, Kandala NB, Currie A, Peile E, Stranges S, Miller MA. 2008. Sleep. Meta-analysis of short sleep duration and obesity in children and adults. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine

Practical note

Graded low: one large accelerometer cohort (UK Biobank, 60,977 participants, mean age about 63) plus a 2020 systematic review of 41 observational studies whose authors rated the evidence very low to moderate with GRADE; no trial has tested changing regularity.

Sources

• Supports“Higher sleep regularity was associated with a 20%-48% lower risk of all-cause mortality” (Abstract) Windred DP, Burns AC, Lane JM, Saxena R, Rutter MK, Cain SW, Phillips AJK. 2024. Sleep. Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study. CC BY (per Europe PMC); credit Windred et al., Sleep 2024; Courtesy of the U.S. National Library of Medicine
• Supports“Findings suggest that later sleep timing and greater sleep variability were generally associated with adverse health outcomes.” (Abstract) Chaput JP, Dutil C, Featherstone R, Ross R, Giangregorio L, Saunders TJ, Janssen I, Poitras VJ, Kho ME, Ross-White A, Zankar S, Carrier J. 2020. Applied Physiology, Nutrition, and Metabolism. Sleep timing, sleep consistency, and health in adults: a systematic review. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine
• Context“Sleep regularity was a stronger predictor of all-cause mortality than sleep duration” (Abstract) Windred DP, Burns AC, Lane JM, Saxena R, Rutter MK, Cain SW, Phillips AJK. 2024. Sleep. Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study. CC BY (per Europe PMC); credit Windred et al., Sleep 2024; Courtesy of the U.S. National Library of Medicine
• Context“The quality of evidence ranged from "very low" to "moderate" across study designs and health outcomes using GRADE.” (Abstract) Chaput JP, Dutil C, Featherstone R, Ross R, Giangregorio L, Saunders TJ, Janssen I, Poitras VJ, Kho ME, Ross-White A, Zankar S, Carrier J. 2020. Applied Physiology, Nutrition, and Metabolism. Sleep timing, sleep consistency, and health in adults: a systematic review. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine

Practical note

Graded moderate: experimental studies with controlled sleep deprivation, pooled across 70 articles and 147 cognitive tests; downgraded from high for heterogeneity between studies and indirectness of total deprivation to everyday partial short sleep.

Safety note

Lapses in attention after sleep loss are relevant to driving and other safety-critical tasks.

Sources

• Supports“Effect sizes ranged from small and nonsignificant (reasoning accuracy: g = -0.125, 95% CI [-0.27, 0.02]) to large (lapses in simple attention: g = -0.776, 95% CI [-0.96, -0.60], p < .001).” (Abstract) Lim J, Dinges DF. 2010. Psychological Bulletin. A meta-analysis of the impact of short-term sleep deprivation on cognitive variables. publisher copyright; metadata and short quotes only; Courtesy of the U.S. National Library of Medicine