Sleep and Health

Sleep is often one of the first things to go when people feel pressed for time. Many view sleep as a luxury and think that the benefits of limiting the hours they spend asleep outweigh the costs. People often overlook the potential long-term health consequences of insufficient sleep, and the impact that health problems can ultimately have on one's time and productivity.

Many of the costs of poor sleep go unnoticed. Medical conditions, such as obesity, diabetes, and cardiovascular disease, develop over long periods of time and result from a number of factors, such as genetics, poor nutrition, and lack of exercise. Insufficient sleep has also been linked to these and other health problems, and is considered an important risk factor. Although scientists have just begun to identify the connections between insufficient sleep and disease, most experts have concluded that getting enough high-quality sleep may be as important to health and well-being as nutrition and exercise.

Risk Assessment

Determining the risks posed by insufficient sleep is complicated. Medical conditions are slow to develop and have multiple risk factors connected to them. What we do know is that sleeping fewer than about eight hours per night on a regular basis seems to increase the risk of developing a number of medical conditions. The study results below show that reducing sleep by just two or three hours per night can have dramatic health consequences.

• Obesity—Several studies have linked insufficient sleep and weight gain. For example, one study found that people who slept fewer than six hours per night on a regular basis were much more likely to have excess body weight, while people who slept an average of eight hours per night had the lowest relative body fat of the study group.¹ Another study found that babies who are "short sleepers" are much more likely to develop obesity later in childhood than those who sleep the recommended amount.²
• Diabetes—Studies have shown that people who reported sleeping fewer than five hours per night had a greatly increased risk of having or developing type 2 diabetes.³,⁴ Fortunately, studies have also found that improved sleep can positively influence blood sugar control and reduce the effects of type 2 diabetes.⁵



• Cardiovascular disease and hypertension—A recent study found that even modestly reduced sleep (six to seven hours per night) was associated with a greatly increased the risk of coronary artery calcification, a predictor of future myocardial infarction (heart attack) and death due to heart disease.⁶ There is also growing evidence of a connection between sleep loss caused by obstructive sleep apnea and an increased risk of cardiovascular diseases, including hypertension, stroke, coronary heart disease, and irregular heartbeat.⁷
• Immune function—Interactions between sleep and the immune system have been well documented. Sleep deprivation increases the levels of many inflammatory mediators, and infections in turn affect the amount and patterns of sleep.⁸ While scientists are just beginning to understand these interactions, early work suggests that sleep deprivation may decrease the ability to resist infection (see The Common Cold, below).
• Common Cold – In a recent study, people who averaged less than seven hours of sleep a night were about three times more likely to develop cold symptoms than study volunteers who got eight or more hours of sleep when exposed to the cold-causing rhinovirus. In addition, those individuals who got better quality sleep were the least likely to come down with a cold. ⁹

Not surprisingly, these potential adverse health effects can add up to increased health care costs and decreased productivity. More importantly, insufficient sleep can ultimately affect life expectancy and day-to-day well-being. An analysis of data from three separate studies suggests that sleeping five or fewer hours per night may increase mortality risk by as much as 15 percent.¹⁰

Not getting enough sleep alters insulin resistance, which is associated with an increased risk of developing type 2 diabetes, and that can be very quickly induced by a single night's total sleep loss.

-Dr. Ann E. Rogers

Sleeping Well, Staying Healthy

While sleeping well is no guarantee of good health, it does help to maintain many vital functions. One of the most important of these functions may be to provide cells and tissues with the opportunity to recover from the wear and tear of daily life. Major restorative functions in the body such as tissue repair, muscle growth, and protein synthesis occur almost exclusively during sleep.

Many other conclusions about the role sleep plays in maintaining health have come from studying what happens when humans and other animals are deprived of the sleep they need. For example, scientists have discovered that insufficient sleep may cause health problems by altering levels of the hormones involved in such processes as metabolism, appetite regulation, and stress response.¹¹,¹²,¹³ Studies such as these may one day lead to a better understanding of how insufficient sleep increases disease risk.

In the meantime, sleep experts say there is ample evidence that shows that when people get the sleep they need, they will not only feel better, but will also increase their odds of living healthier, more productive lives.

References

1. Kohatsu ND, et al. Sleep Duration and Body Mass Index in a Rural Population, Archives of Internal Medicine. 2006 Sep 18; 166(16): 1701.
2. Taveras EM, et al. Short Sleep Duration in Infancy and Risk of Childhood Overweight, Archives of Pediatrics & Adolescent Medicine. 2008 Apr; 162(4): 305.
3. Knutson KL, et al. Role of Sleep Duration and Quality in the Risk and Severity of Type 2 Diabetes Mellitus, Archives of Internal Medicine. 2006 Sep 18; 166(16):1768.
4. Gottlieb DJ, et al. Association of Sleep Time with Diabetes Mellitus and Impaired Glucose Tolerance, Archives of Internal Medicine. 2005 Apr 25; 165(8): 863.
5. Nilsson PM, et al. Incidence of Diabetes in Middle-Aged Men Is Related to Sleep Disturbances, Diabetes Care. 2004; 27(10): 2464.
6. King, CR et al. Short Sleep Duration and Incident Coronary Artery Calcification, JAMA, 2008: 300(24): 2859-2866.
7. Kasasbeh E, et al. Inflammatory Aspects of Sleep Apnea and Their Cardiovascular Consequences, South Med J. 2006 Jan; 99(1): 58-67.
8. Opp, MR, et al. Neural-Immune Interactions in the Regulation of Sleep, Front Biosci. 2003 May 1;8:d768-79.
9. Cohen S, et al. Sleep Habits and Susceptibility to the Common Cold, Arch of Intern Med. 2009 Jan 12; 169 (1):62-67.
10. Colten HR and Altevogt BM, eds. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Board on Health Sciences Policy; National Academies Press. 2006.
11. Spiegel K, et al. Brief Communication: Sleep Curtailment in Healthy Young Men Is Associated with Decreased Leptin Levels, Elevated Ghrelin Levels, and Increased Hunger and Appetite, Annals of Internal Medicine. 2004 Dec 7; 141(11): 846-850.
12. Spiegel K, et al. Impact of Sleep Debt on Metabolic and Endocrine Function, Lancet. 1999 Oct 23: 354(9188): 1435-9.
13. Meier-Ewert HK, et al. Effect of Sleep Loss on C-reactive Protein, an Inflammatory Marker of Cardiovascular Risk, J Am Coll Cardiol. 2004 Feb 18; 43(4): 678-83.