We all need a good night’s rest. Sleep refreshes and energizes us, and enables us to take on the day. Adults need seven to nine hours of sleep a night, yet the average American usually manages just six-and-half hours. The Centers for Disease Control and Prevention (CDC) recognizes sleep insufficiency as a public health problem. More than a quarter of all Americans report not getting enough sleep, and 10 percent experience chronic insomnia. Many of these sleepyheads may not “just” be stressed, but may actually have an underlying sleep disorder.

Here’s why that’s a problem.

Sleep Basics

Have you ever heard the old adage that every hour spent asleep before midnight was worth two hours spent asleep after midnight? While not entirely accurate, it does have some basis in the very different phases of a sleep cycle.

There are two types of sleep: non-rapid eye movement (NREM) and rapid eye movement (REM). There are three stages to NREM. As we start to fall asleep, we enter N1, where the eye and muscle activity begins to slow, your mind drifts, but you can awaken easily. In N2, you become less aware of your surroundings, the brain waves become slower, and body temperature drops. N3—also known as slow wave sleep (SWS)—is the deepest and most restorative stage of sleep, during which it is most difficult to be awakened. SWS positively affects the whole of our nervous system: our heart rate slows, gland activity increases, and deep intestinal muscles relax, all of which aids our digestive processes, regulates important hormone production, and even strengthens our immune system. What’s more, SWS is also associated with memory consolidation, the ability to learn, and mental alertness for the next day.

During REM sleep, breathing, heart rate, and blood pressure increases, our eyes shift around and we begin to dream. A complete sleep cycle takes roughly 90 minutes. The first sleep cycles in a night have relatively short REM stages and longer SWS—where the grain of truth in the above adage is based—but as the night progresses, this shifts and the REM period is extended.

While individual sleep needs vary, the following sleep guidelines from the National Sleep Foundation are a good starting point:

The timing, quantity of, and quality of sleep can affect endocrine (hormone production), metabolic, and neurohormanal (hormones not made by the endocrine system but by nerve cells) functions related to health. Sleep is an active and restorative time for the body.

Physical Risks

Insufficient sleep can be dangerous. Short-term sleep deprivation can lead to car- or machinery-related accidents, resulting in injury and/or disability. Long-term sleep deprivation can lead to weight gain, obesity, diabetes, hypertension, heart attack, stroke, decreased immunity, the development of some types of cancer, and depression.

Weight gain

Several studies^{1, 2} have indicated that insuffient sleep (less than five or six hours) and excessive sleep (more than nine or ten hours) are associated with weight gain. Studies³ of identical and fraternal twins suggest there is a genetic component: while all of us have a bunch of genes that may or may not get “turned on,” sleep deprivation can lead to the expression—or “awakening”—of those genes that are related to obesity.

Sleep deprivation can also affect the hormones that regulate appetite. Ghrelin increases appetite and plays a role in body weight. Leptin decreases appetite, increases energy expenditure, and promotes fat utilization. Chronic sleep loss can cause an increase in the ratio of ghrelin to leptin, enhancing appetite and specifically increasing cravings for carbohydrate foods, resulting in weight gain over time.¹

Impairment of Glucose Metabolism

Evidence shows that sleep quality, quantity, and timing may also affect the 24-hour patterns of hormone production, such as insulin, cortisol, glucagon, catecholamines, and growth hormone, along with the appetite-regulating hormones, leptin and ghrelin.⁵ Lack of sleep, specifically SWS, can cause impaired glucose tolerance, which can increase your risk of diabetes.

Cardiovascular disease

Sleep apnea—a serious sleep disorder in which breathing pauses and restarts repeatedly— has been found to increase the risk of a number of cardiovascular diseases such as hypertension (high blood pressure), stroke, coronary heart disease, and irregular heartbeat.

Depression

Sleep disorders have traditionally been considered a symptom of depression, but recent research shows it might actually work the other way around, too: effectively treating sleep disturbances, such as sleep apnea, can result in a decrease of the symptoms of depression.

Cancer

Recent research has shown a relationship between insufficient sleep and top cancers in the United States, such as prostate cancer, colorectal cancer, and breast cancer.⁶ Research also suggests that people with sleep apnea have an increased risk of developing any type of cancer. Lack of sleep increases inflammation and disrupts normal immune function, both of which may promote the development of cancer. Additionally, melatonin, which is produced during sleep, may have antioxidant properties that help prevent cellular damage.⁷

Children

Insufficient sleep in children appears to have negative metabolic effects, such as impaired insulin sensitivity—which could lead to diabetes —and the development of cardiovascular disease markers such as increased LDL. Research shows a strong correlation between inadequate sleep in children and a higher body mass index (BMI), a screening tool to determine your risk of heart disease, diabetes, and other chronic health problems. ^1,2 Additionally, there is a clear link between obesity, sleep disturbance breathing, and metabolic syndrome in children and adolescents.⁴

More than just a way to feel good and refreshed, sleep is clearly a vital component of any healthy lifestyle. If you’re not getting enough shut-eye on a regular basis, it may be time to prioritize how to do so, such as by limiting factors that disturb sleep—the usual suspects like caffeine, nicotine, and alcohol—and being disciplined about getting to bed in time to clock in your recommended nightly allowance.

If you’re having problems falling or staying asleep, try some of the useful sleep tips. Your mind and body will thank you for it.

Sleep Tips

1. Go to bed at the same time each night and rise at the same time every morning—even on the weekends.
2. Exercise during the day 30 to 60 minutes most days of the week.
3. Avoid caffeine, nicotine, and alcohol, as they can stimulate the nervous system, interfere with falling asleep and staying asleep by increasing heart rate, blood pressure, and adrenaline levels.
4. Get 30 minutes of sunlight exposure, ideally 10 minutes in the morning and another 20 minutes or more in the afternoon.
5. Take a nap if needed but not more than 20 minutes or past 3pm.
6. Keep eating and drinking to small quantities before bedtime.
7. Avoid electronics, including TV and computer, at least one hour before bedtime.
8. Reduce the electromagnetic smog by eliminating electronics (TVs, tablets, smartphones, etc.) from the bedroom. If you need an alarm clock, use an old-fashioned, battery-operated alarm clock.
9. Create a bed that appeals: consider mattress firmness, blankets, and sheets that are most comfortable for you.
10. Sleep in complete darkness. Use blackout shades or heavy curtains if necessary to eliminate light that comes in from outside sources.
11. Make your bedroom as quiet as possible. If there’s outside noise, try a white noise machine or a fan to create a constant background noise.
12. Keep your bedroom cool, ideally 60- 70 degrees Farenheit. Our body naturally drops when we sleep.
13. Some people benefit from aromatherapy. Try a therapeutic-grade lavender essential oil in a cool diffuser.
14. Consider taking melatonin, particularly if you’re a shift worker who must sleep during the day instead of at night.

References:

1. Morselli LL, Guyon A, Spiegel K. Sleep and metabolic function.Pflügers Arch. 2012;463(1):139-160.
2. Chaput JP, Després JP, Bouchard C, Tremblay A. The association between sleep duration and weight gain in adults: a 6-year prospective study from the Quebec Family Study.Sleep. 2008;31(4):517-523.
3. Watson NF, Harden P, Buchwald D, Schur E., Goldberg J. Sleep duration modifies the heritability of body mass index. Poster presented at the Annual Meeting of the Associated Professional Sleep Societies LLC, 2011.http://www.journalsleep.org/Resources/Documents/2011abstractsupplement.pdf. Accessed March 28, 2012.
4. Verhulst SL, Franckx H, Van Gaal L, De Backer W, Desager K. The effect of weight loss on sleep-disordered breathing in obese teenagers.Obesity (Silver Spring). 2009;17(6):1178-1183
5. http://www.todaysdietitian.com/newarchives/060112p48.shtml
6. http://www.cancercenter.com/community/newsletter/article/researchers-are-studying-the-link-between-sleep-and-cancer/
7. http://www.researchgate.net/profile/David_Blask/publication/23676435_Melatonin_sleep_disturbance_and_cancer_risk/links/542d70560cf277d58e8cc557.pdf