The American Academy of Sleep Medicine and Sleep Research Society guidelines for healthy sleep advise that sleep is essential for good health.1 They recommended that adults sleep seven hours or more per night on a regular basis. Similarly, guidelines from the National Sleep Foundation recommend that adults get 7-9 hours of high quality sleep each night.2,3 Sleep quality and duration has been found to be integral to cardiovascular health, leading to the American Heart Association (AHA) adding it to Life’s Simple 7 in 2022 to form Life’s Essential 8.4 AHA guidance recommends 7-9 hours of high quality sleep each night for optimal cardiovascular health.
National Sleep Foundation guidelines advise that sleep duration recommendations vary widely based on age.3 For example, the appropriate sleep duration for newborns is 14-17 hours, infants 12-15 hours, toddler 11-14 hours, preschoolers 10-13 hours, and school-aged children 9-11 hours. Recommendations for teenagers are looser, with National Sleep Foundation guidelines advising 8-10 hours and the American Academy of Sleep and Sleep Research Society guidelines stating that nine or more hours of sleep can be appropriate.1,3
Sleeping less than seven hours each night is associated with a host of negative health effects such as cardiovascular disease (CVD)4; metabolic dysfunction including weight gain, obesity, and diabetes5-7; increased inflammation and inflammatory markers8; mental impairment including higher risk of accidents9; and all-cause mortality.10,11
Evidence is inconclusive about the health risks of adults sleeping more than nine hours per night on a regular basis.1 Although there is an association between sleeping more and health risks in adults, the relationship has not been shown to be causative, and some health conditions can cause increased sleep duration. Additionally, for those recovering from sleep debt and those with certain medical conditions, sleeping more than nine hours may be appropriate.
Cardiovascular Disease
A 2024 study extracted data from the National Health and Nutrition Examination Survey database to evaluate the relationship between poor quality sleep and risk of coronary heart disease and stroke in 6,830 individuals over the age of 40 years (1,001 with CVD).12 Those without CVD were more likely to report getting an optimal amount of sleep (7-8 hours per night; 51.04% vs 11.79%, p<0.01). Conversely, those with CVD were more likely to report getting <7 hours of sleep per night (44.56% vs 20.31%, p<0.01), >8 hours of sleep per night (43.66% vs 28.65%, p<0.01), and daytime sleepiness (68.33% vs 16.19%, p<0.01). Those with CVD were also more likely to have contributors to poor sleep, including snoring (87.31% vs 47.35%, p<0.01) and having a later bedtime (after 11 PM; 68.03% vs 44.76%, p<0.01).
Metabolic Dysfunction
A 2002 analysis of data from the Cancer Prevention Study II, conducted from 1982-1988, found that less sleep was associated with increased body mass index (BMI).13 Among women (n=636,095), those sleeping four hours had a 1.39 kg/m2 greater BMI than those sleeping seven hours. The same trend was true for men (n=480,841), but to a lesser extent, with men sleeping four hours having a 0.57 kg/m2 greater BMI than those sleeping seven hours.
A prospective cohort study of 35,247 Japanese adults followed from 2006-2007 found that shorter sleep was significantly associated with increased BMI.14 The average BMI was 24.4 among those who slept less than five hours compared to 23.6 for those sleeping 7-8 hours (p<0.001). Similarly, the incidence of obesity was higher among those who slept less, with 43.8% of those sleeping less than five hours having obesity compared to 33.3% of those sleeping 7-8 hours (p<0.001).
A prospective study of data from the Nurses’ Health Study (n=70,026) found that both BMI and incidence of type 2 diabetes was higher among those who slept less.15 At baseline, BMI was 25.2 for those that reported sleeping less than five hours compared to 24.4 for seven hours and 24.5 for eight hours of sleep. Over ten years of follow-up, the incidence of newly diagnosed type 2 diabetes was 4.3 per 1,000 person-years for less than five hours of sleep (adjusted Relative Risk [RR] 1.18, 95% Confidence Interval [CI] [1.28-1.92]) compared to 2.6 and 2.7 per 1,000 person-years for seven and eight hours of sleep, respectively (adjusted RR 0.98, 95% CI [0.87-1.11] for seven hours; eight hours used as reference).
Inflammation
Not receiving adequate sleep has been shown to lead to a proinflammatory state with elevations in inflammatory markers. A 2013 cross-sectional study of data from the Whitehall II study (n=5,003) found that shorter sleep duration was associated with significantly increased levels of both C-reactive protein and interleukin-6 (IL-6).16 Among those who slept five hours or less, the mean measure of C-reactive protein was 1.47 mg/L compared to 1.28 mg/L for seven hours (p<0.05) and 1.20 mg/dL for eight hours of sleep (p<0.01). Similarly, IL-6 levels were a mean of 1.85 µg/L for five hours or less of sleep compared to 1.70 and 1.69 for seven and eight hours of sleep, respectively (p<0.01).
Mental Impairment
Several studies have found that inadequate sleep can lead to decreased mental acuity, which can in turn lead to increased incidence of accidents and injuries. A 2012 cross-sectional study of farm workers from Saskatchewan (n=4,323) found that less sleep was associated with higher incidence of work injury.17 Those who slept five hour or less each night had an 8.9% incidence of injuries during peak season compared to 4.0% among those who slept seven hours or more each night (p<0.001).
Mortality
The impact of sleep on health have been described for decades. The American Cancer Society’s first Cancer Prevention Study published in 1964 (n=1,064,004) found that a report of insomnia was associated with 32% higher mortality in the following year compared to people who did not report insomnia (mortality ratio 1.32; 1,715 observed vs. 1,303 expected deaths among 890,394 adults).18
References
- Watson NF, Badr MS, Belenky G, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep. Jun 1 2015;38(6):843-4. doi:10.5665/sleep.4716
- Ohayon M, Wickwire EM, Hirshkowitz M, et al. National Sleep Foundation's sleep quality recommendations: first report. Sleep Health. Feb 2017;3(1):6-19. doi:10.1016/j.sleh.2016.11.006
- Hirshkowitz M, Whiton K, Albert SM, et al. National Sleep Foundation's updated sleep duration recommendations: final report. Sleep Health. Dec 2015;1(4):233-243. doi:10.1016/j.sleh.2015.10.004
- Lloyd-Jones DM, Allen NB, Anderson CAM, et al. Life's Essential 8: Updating and Enhancing the American Heart Association's Construct of Cardiovascular Health: A Presidential Advisory From the American Heart Association. Circulation. Aug 2 2022;146(5):e18-e43. doi:10.1161/cir.0000000000001078
- Morselli LL, Guyon A, Spiegel K. Sleep and metabolic function. Pflugers Arch. Jan 2012;463(1):139-60. doi:10.1007/s00424-011-1053-z
- Knutson KL. Does inadequate sleep play a role in vulnerability to obesity? Am J Hum Biol. May-Jun 2012;24(3):361-71. doi:10.1002/ajhb.22219
- Shan Z, Ma H, Xie M, et al. Sleep duration and risk of type 2 diabetes: a meta-analysis of prospective studies. Diabetes Care. Mar 2015;38(3):529-37. doi:10.2337/dc14-2073
- Grandner MA, Sands-Lincoln MR, Pak VM, Garland SN. Sleep duration, cardiovascular disease, and proinflammatory biomarkers. Nat Sci Sleep. 2013;5:93-107. doi:10.2147/nss.S31063
- Goel N, Rao H, Durmer JS, Dinges DF. Neurocognitive consequences of sleep deprivation. Semin Neurol. Sep 2009;29(4):320-39. doi:10.1055/s-0029-1237117
- Cappuccio FP, D'Elia L, Strazzullo P, Miller MA. Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep. May 2010;33(5):585-92. doi:10.1093/sleep/33.5.585
- Gallicchio L, Kalesan B. Sleep duration and mortality: a systematic review and meta-analysis. J Sleep Res. Jun 2009;18(2):148-58. doi:10.1111/j.1365-2869.2008.00732.x
- Hou XZ, Li YS, Wu Q, et al. Association of sleep characteristics with cardiovascular disease risk in adults over 40 years of age: a cross-sectional survey. Front Cardiovasc Med. 2024;11:1308592. doi:10.3389/fcvm.2024.1308592
- Kripke DF, Garfinkel L, Wingard DL, Klauber MR, Marler MR. Mortality associated with sleep duration and insomnia. Arch Gen Psychiatry. Feb 2002;59(2):131-6. doi:10.1001/archpsyc.59.2.131
- Watanabe M, Kikuchi H, Tanaka K, Takahashi M. Association of short sleep duration with weight gain and obesity at 1-year follow-up: a large-scale prospective study. Sleep. Feb 2010;33(2):161-7. doi:10.1093/sleep/33.2.161
- Ayas NT, White DP, Al-Delaimy WK, et al. A prospective study of self-reported sleep duration and incident diabetes in women. Diabetes Care. Feb 2003;26(2):380-4. doi:10.2337/diacare.26.2.380
- Ferrie JE, Kivimäki M, Akbaraly TN, et al. Associations between change in sleep duration and inflammation: findings on C-reactive protein and interleukin 6 in the Whitehall II Study. Am J Epidemiol. Sep 15 2013;178(6):956-61. doi:10.1093/aje/kwt072
- Lilley R, Day L, Koehncke N, Dosman J, Hagel L, William P. The relationship between fatigue-related factors and work-related injuries in the Saskatchewan Farm Injury Cohort Study. Am J Ind Med. Apr 2012;55(4):367-75. doi:10.1002/ajim.22003
- Hammond EC. SOME PRELIMINARY FINDINGS ON PHYSICAL COMPLAINTS FROM A PROSPECTIVE STUDY OF 1,064,004 MEN AND WOMEN. Am J Public Health Nations Health. Jan 1964;54(1):11-23. doi:10.2105/ajph.54.1.11
