It may seem obvious that sleep is beneficial. Even without fully grasping what sleep does for us, we know that going without sleep for too long makes us feel terrible, and that getting a good night’s sleep can make us feel ready to take on the world. When we awaken from a restful sleep, we feel more alert, more energetic, happier, and better able to function. However, the fact that sleep makes us feel better and that going without sleep makes us feel worse only begins to explain why sleep might be necessary. Numerous studies have linked poor sleep with an increased risk of cardiovascular disease, a weakened immune system, cancers, high blood pressure, obesity and Type 2 diabetes.
Despite its benefits, far too many Americans are chronically sleep deprived. We live in very stressful times. One-third of Americans are losing sleep over the state of the U.S. economy and other personal financial concerns.[1] According to the National Sleep Foundation, 20 percent of us get less than 6 hours sleep a night. For many others, a good night’s sleep is increasingly losing out to the distractions and extremely hectic nature of our modern life. Some hard-charging professionals even shun regular sleep in deference to the philosophy “I’ll sleep when I am dead”. Well it turns out that getting enough sleep, and other kinds of rest, just might postpone when your death occurs as well as increase the effectiveness and joyfulness of your life.
One way to think about the function of sleep is to compare it to another of our life-sustaining activities: eating. Hunger is a protective mechanism that has evolved to ensure that we consume the nutrients our bodies require to grow, repair tissues, and function properly. Both eating and sleeping are regulated by powerful internal drives. Going without food produces the uncomfortable sensation of hunger, while going without sleep makes us feel overwhelmingly sleepy. And just as eating relieves hunger and ensures that we obtain the nutrients we need; sleeping relieves sleepiness and ensures that we obtain the sleep we need.
Insufficient sleep may alter crucial hormone functions and energy expenditures. A recent study found that a restriction in the amount of sleep time compromised the effectiveness of a reduced calorie diet for weight loss and reduction of metabolic risk factors.[2] Another study found that sleep deprivation was associated with a two-fold risk of being obese in children and adults. That research also suggested that those who slept less have a greater increase in body mass index and waist circumference over time and a greater chance of becoming obese over time.[3] Obesity has, in turn, been linked to a variety of chronic and life-threatening diseases, including sleep apnea; a common disorder in which the upper airway is intermittently narrowed or blocked, disrupting sleep and breathing during sleep. Researchers from the Sleep Heart Health Study found that sleep apnea doubled the risk for strokes in men, and increased the danger for women.[4]
Physiologic studies suggest that a sleep deficit may put the body into a state of high alert, increasing the production of stress hormones and driving up blood pressure, a major risk factor for heart attacks and strokes. Moreover, people who are sleep-deprived have elevated levels of substances in the blood that indicate a heightened state of inflammation in the body, which has also emerged as a major risk factor for heart disease, stroke, cancer and diabetes. Other studies have found that sleep influences the functioning of the lining inside blood vessels, which could explain why people are most prone to heart attacks and strokes during early morning hours.[5] The strongest evidence seems to be linking sleep deprivation to an increased mortality risk. Otherwise healthy people who do not get enough sleep or who shift their sleep schedules because of work, family or lifestyle appeared to be significantly more likely to die sooner.
How much sleep is enough? Generally, experts recommend seven to nine hours per night. But, as it turns out there is no absolute number of hours. Everyone requires more or less sleep depending on a variety of factors including your individual makeup as well as your lifestyle. What counts is that you are getting enough sleep for your body and mind to be replenished, whether that is six, seven, or eight hours or more.
[1] National Sleep Foundation, Sleep in America Poll, 2009
[2] Nedeltcheva A, Kilkus J, et al. “Insufficient Sleep Undermines Dietary Efforts to reduce Adiposity”. Ann Int Med. October 5, 2010
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[3] Cappuccio F, et al. “Sleep Deprivation Doubles Risks Of Obesity In Both Children And Adults.” ScienceDaily 13 July 2006.
[4] Redline S, Yenokyan G, et al. Obstructive Sleep Apnea- Hypopnea and Incident Stroke. American Journal of Respiratory and Critical Care Medicine Vol 182. pp. 269-277, (2010)
[5] Wolfe B, Volzke H, et al. Relation of Self-reported Sleep Duration with Carotid Intima Media Thickness in a General Population Sample. Eur J Cardiovasc Prev Rehab. Volume 196, Issue 2, Pages 727-732 (February 2008)
