Why Better Sleep = Better Health

Good sleep benefits health, longevity, and quality of life.


Why Everyone Needs Sufficient Sleep

The amount of sleep needed to feel well-rested and fully alert in waking hours varies from person to person, and from infancy to adulthood. Most adults feel and perform best with about 7 to 8 hours of sleep per day, ideally at night, when humans sleep best. Sufficient sleep also benefits overall health.

The average American adult sleeps less than 7 hours per night, about an hour less than adults in the U.S. reportedly averaged 50 years ago.

Many aspects of modern life compete with the basic biological need for sleep. These include the increased use of artificial lighting, 24-hour cable television and Internet availability, and a global economy that requires a 24-hour workforce.

Train operators, pilots, truckers, and other transportation workers responding to the 2012 National Sleep Foundation Poll reported averaging less than 7 hours of sleep per night. Other surveys yield similar findings for U.S. adults in a variety of occupations, suggesting society as a whole obtains insufficient sleep.

Sleep serves a vital function, however. Adults who habitually sleep less than 7 to 8 hours have an increased risk of developing serious medical disorders. These include obesity, diabetes, heart and blood vessel disease, stroke, and mood disorders.

Several important studies highlight these findings:

  • Obesity: Adults who habitually sleep 6 hours per day or less are more likely to be overweight or obese than those who usually sleep 7 to 8 hours per day. Researchers found that 8-hour sleepers had the lowest relative body fat of all those in the study group.1

Other studies highlight the value of promoting good sleep from early in life. Researchers found that children aged 6 to 24 months who averaged less than 12 hours of sleep per day had a higher likelihood of being overweight at 3 years of age. Children who slept the least and watched the most television had the highest odds of becoming overweight later on.2

Sleep Deprivation (01:08)
Ann E. Rogers, PhD, RN, of the University of Pennsylvania School of Nursing, discusses sleep deprivation, weight gain, and diabetes.

  • Diabetes: People who reported sleeping fewer than 5 hours per day were found to have an increased risk of developing type 2 diabetes. In this disorder, formerly called adult-onset diabetes, cells fail to use insulin properly.3,4 Researchers found that improved sleep led to better blood sugar control, and reduced symptoms of this disorder.5
  • Heart and blood vessel disease, and high blood pressure: Researchers found people who averaged sleeping 6 to 7 hours per day had a higher risk of coronary artery calcification, a disorder linked to future heart attacks and death from heart disease, than people who slept 7 to 8 hours on average.6 People with obstructive sleep apnea (OSA), who experience markedly disrupted sleep, have an increased risk of heart and blood vessel diseases, including high blood pressure, stroke, coronary heart disease, and irregular heartbeat.7

Sleep Deprivation and Cardiovascular Risk (00:31)
Janet Mullington, PhD, of Harvard, tells how sleep deprivation increases the risk of heart and blood vessel disease.

  • Immune function and colds: Sleep deprivation may decrease the ability to resist infection.8 When exposed to the cold-causing rhinovirus, people who averaged less than 7 hours of sleep per day were 3 times more likely to develop cold symptoms than those who averaged 8 hours or more. People with good quality sleep developed fewer colds than those with poor quality sleep.9

Sleep and Health (00:36)
Orfeu Buxton, PhD, of Harvard, describes animal and human studies that suggest adequate sleep promotes a long and healthy life.

  • Life Expectancy: Sleeping 5 or fewer hours per day may decrease life expectancy by as much as 15 percent, when compared to sleeping 7 to 8 hours per day.10

  • Sleep and Mood: Poor or inadequate sleep may cause irritability and stress, while healthy sleep can boost one's sense of well-being. Chronic insomnia may increase the risk of developing depression and anxiety.11,12

Sleep and Mood (00:49)
Lawrence Epstein, MD, of Harvard, describes links between sleep and mood.


  1. Kohatsu ND, Tsai R, Young T, VanGilder R, Burmeister LF, Stromquist AM, Merchant JA. Sleep duration and body mass index in a rural population. Arch Intern Med 2006 Sep 18;166(16):1701-5.
  2. Taveras EM, Rifas-Shiman SL, Oken E, Gunderson EP, Gillman MW. Short sleep duration in infancy and risk of childhood overweight. Arch Pediatr Adolesc Med 2008 Apr;162(4):305-11.
  3. Knutson KL, Ryden AM, Mander BA, Van Cauter E. Role of sleep duration and quality in the risk and severity of type 2 diabetes mellitus. Arch Intern Med 2006 Sep 18;166(16):1768-74.
  4. Gottlieb DJ, Punjabi NM, Newman AB, Resnick HE, Redline S, Baldwin CM, Nieto JF. Association of sleep time with diabetes mellitus and impaired glucose tolerance. Arch Intern Med 2005 Apr 25;165(8):863-67.
  5. Nilsson PM, Rööst M, Engström G, Hedblad B, Berglund G. Incidence of diabetes in middle-aged men is related to sleep disturbances. Diabetes Care 2004 Oct;27(10):2464-69.
  6. King CR, Knutson KL, Rathouz PJ, Sidney S, Liu K, Lauderdale DS. Short sleep duration and incident coronary artery calcification. JAMA 2008;300(24):2859-66.
  7. Kasasbeh E, Chi DS, Krishnaswamy G. Inflammatory aspects of sleep apnea and their cardiovascular consequences. South Med J 2006 Jan;99(1):58-67.
  8. Opp MR, Toth LA. Neural-immune interactions in the regulation of sleep. Front Biosci 2003 May 1;8:d768-79.
  9. Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. Sleep habits and susceptibility to the common cold. Arch Intern Med 2009 Jan 12;169(1):62-67.
  10. Colten HR, Altevogt BM, eds. Sleep disorders and sleep deprivation: An unmet public health problem. Board on Health Sciences Policy; National Academies Press. 2006.
  11. Baglioni C, Battagliese G, Feige B, Spiegelhalder K, Nissen C, Voderholzer U, Lombardo C, Riemann D. Insomnia as a predictor of depression: a meta-analytic evaluation of longitudinal epidemiological studies. J Affect Disord. 2011 Dec;135(1-3):10-9. Epub 2011 Feb 5.12.
  12. Léger D, Bayon V. Societal costs of insomnia. Sleep Med Rev. 2010 Dec;14(6):379-89. Epub 2010 Mar 31.

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This content was last reviewed on June 6, 2012