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New Research Links Good Sleep to Good Health

Lack of sleep may contribute to obesity, heart disease and frequent colds.

The country’s financial woes have found their way into the bedroom.

Poll results released by the National Sleep Foundation (NSF) in early March find that one-third of Americans are losing sleep over worries about the economy, personal finances and health care costs. The restless nights might be harming their health as well.

It’s no secret that sleep is essential to health—it rests the body, renews the brain and produces higher levels of certain beneficial hormones. Unfortunately, getting those often-recommended seven to eight hours of sound, restful sleep—night after night—may be something you can only dream about.

By around age 60, it may take even longer to fall asleep—and stay asleep. The NSF says that nearly half of older people report they have insomnia several nights a week or more.

Sometimes, bad sleep is the result of health conditions—from those midnight bathrooms breaks triggered by an enlarged prostate to the pain of arthritis, fibromyalgia and other ailments. But even perfectly healthy people in their later years may find themselves dosing off in the daytime and tossing and turning at night.

“As you age, different physiologic processes take place in the body that affect sleep,” explains Aparajitha Verma, M.D., medical director of the Sleep Disorders Center at the Methodist Hospital in Houston. “The circadian rhythm of older people—your internal body clock—changes, so you may be sleepier in the daytime and have lower sleep efficiency at night.”

But that may be OK, say some experts. In one study published last August in Current Biology, researchers from Harvard’s Brigham and Women’s Hospital and from the United Kingdom reported that otherwise healthy people sleep less as they get older because they need less shuteye—about 1.5 hours less per night for those in their 60s compared with twentysomethings. Why less sleep? Because of a shifting circadian rhythm, more daytime napping and, often, a lower daytime expenditure of energy.

“Some people need more sleep, some people need less: A specific person’s individual sleep requirement is just that—very individual,” notes Verma. “But for most people, it’s clear that not getting seven or eight hours a night consistently is related to several health issues such as problems with memory, concentration and learning; poorer physical performance; and a greater risk of traffic accidents.”

But in recent months, several studies provide more evidence that failing to consistently meet the goal of seven to eight hours may further impact some already dangerous age-related conditions:

Blood vessels. Artery-stiffening calcium deposits are twice as likely to occur in people who sleep five to seven hours per night, finds a study published last December in the Journal of the American Medical Association that tracked 495 middle-age men and women for five years. But increasing sleep just one hour per night may cut this risk by about a third—the equivalent of a 16-point drop in blood pressure.

The links between sleep and artery health are still being explored but senior researcher Diane Lauderdale of the University of Chicago has some theories. “Blood pressure tends to dip during sleep, so it’s possible that sleeping longer means that people have relatively lower blood pressure during a 24-hour period,” she says. “Also, when people are sleep deprived, that may release high levels of stress hormones such as cortisol, which we know is a risk factor for heart disease.”

Cholesterol. It’s not clear why, but older people who sleep less than seven hours per night—or more than eight hours—may have higher cholesterol, and lower levels of heart-healthy HDLs, observed Dutch researchers in the November/December 2008 issue of Psychosomatic Medicine. Their study included 768 men and women age 57 and older, none of whom were taking statin drugs.

Heart disease. After tracking more than 58,000 Chinese men and women age 45 and older in Singapore, researchers found that during their 13-year study, those getting less than five hours of sleep—or more than nine hours—were up to twice as likely to die from heart disease compared with those getting about seven hours a night. Researchers who published their study last year in the American Journal of Epidemiology found this link independent of known risk factors such as smoking and obesity.

Colds and respiratory illness. The less sleep you get, the more vulnerable you are to the common cold. In addition, a recent team from three universities—Carnegie Mellon, the University of Pittsburgh and the University of Virginia—wrote in Archives of Internal Medicine that people who get less than seven hours per night are three times more likely to develop respiratory illness after a cold than those sleeping eight hours or more. Researchers suspect that lack of sleep interferes with infection-fighting mechanisms.

Obesity. Emerging evidence suggests that getting too little sleep may play a key role in an expanding waistline, which factors into heart disease, diabetes and other health problems. “We know there’s more daytime snacking in people who are sleep-deprived,” notes Verma, “because sleep helps regulate two hormones affecting appetite—ghrelin, which tells the brain you need to eat more, especially cravings for poor carbohydrate choices; and leptin, which tells the brain that you’re full. People who don’t sleep enough have higher levels of ghrelin.”

In one study presented at a meeting of sleep specialists last year, University of Chicago researchers noted that participants limited to 5.5 hours of sleep per night consumed about 200 extra calories per day on snacks alone compared with those who had “normal” sleep patterns. Other research has found that people who sleep more than nine hours a night are also more likely to be obese.

Diabetes. People who sleep less than six hours a night appear to have a higher risk of developing abnormal blood sugar levels that can lead to type 2 diabetes, according to a study presented March 11 at an American Heart Association conference in Palm Harbor, Fla. Researchers followed 1,455 people over six years and found that those who slept less than six hours a night were nearly five times more likely to develop impaired fasting glucose than those tho slept six to eight hours a night.

So how can you better ensure a sound night’s sleep? Some suggestions from Verma:

    * Get a checkup. Both insomnia and daytime sleepiness are often caused by an underlying medical problem, says Verma. Common culprits include anxiety and depression, as well as sleep apnea—which is “very common, but often undiagnosed, in post-menopausal women.”

    * Avoid sleep aids. Prescription medications offer temporary relief, but can quickly lose their efficacy. “Then they produce a rebound effect so you need them to sleep well,” say Verma. They also can cause dangerous interactions with other medications and some can cause drug dependence.

    * Practice stress management. Studies show that adults who regularly practice tai chi, yoga or other types of mood-boosting exercise sleep better. “Strong family networks and other social interactions also help improve sleep,” notes Verma.

    * Nix the nightcap. Avoid alcohol within four to six hours of bedtime; it can cause “fragmented” sleep when metabolized. Caffeine can also keep you up and worsen restless legs syndrome, which triggers a powerful urge to move your legs (waking you and your bedmate) and can cause a tingling or burning sensation.

    * Time your naps. If you regularly take daytime naps, limit them to 15 to 30 minutes. Any longer and they’ll likely affect nighttime sleep or could indicate an underlying health problem.

Sid Kirchheimer writes about consumer and health issues.