Sleepless nights can cause worse problems than grumpiness

Kathy McCleary

Confession time: My husband has actually uttered the words "I'd rather take a nap than have sex." Is our marriage on the rocks? No, like 75 percent of adults, our problem is sleep -- he has insomnia; I snore.

We seem to be too busy to get enough sleep. On average, Americans sleep roughly 7 hours a night, 1 to 2 fewer hours per night than they did 40 years ago. And when we do hit the sack, sleep doesn't necessarily follow. No wonder my husband and I sometimes feel like zombies. Worse, there could be serious health repercussions due to our lack of shut-eye.

Do you have a sleep disorder?

How much sleep each person needs varies, though the differences may not be as great as you think, says Eve Van Cauter, Ph.D, professor of medicine at the University of Chicago. Studies have shown that sleep capacity -- how long you'll sleep if you go to bed and get up whenever you want -- is about 8 hours and 45 minutes for healthy young males (the group that's been researched most). In three separate studies, that amount varied less than 30 minutes from person to person. "A lot of people who believe they need only 4 hours of sleep are unconsciously depriving themselves," Van Cauter says.

Most people need 7 to 8 hours a night, according to Lawrence Epstein, M.D., regional medical director for Sleep HealthCenters in Boston, Massachusetts, and former president of the American Academy of Sleep Medicine.

"The idea shouldn't be to get into bed, fall asleep instantly, sleep a set number of hours, and wake up never having had your sleep disturbed," he explains. "The target should be to get an adequate amount of sleep to feel rested during the day."

How do you know you're not getting enough z's? "If you're falling asleep in 1 or 2 minutes, you're probably sleep deprived," says Thomas Roth, M.D., director of the Sleep Disorders and Research Center at Henry Ford Hospital in Detroit, Michigan.

On average, it takes most people about 15 minutes to fall asleep, though Roth notes that "it takes some people more time, some people less." Another way to tell if you're not sleeping enough is to monitor daytime sleepiness. Chronic daytime sleepiness is not normal, says Michael Twery, Ph.D., acting director of the National Center on Sleep Disorders Research. "People can live for decades and never appreciate that they have a sleep disorder and how it's affecting their lives."

The downside of running on empty

Scientists are finding more evidence that sleep deprivation can affect appetite, weight gain, diabetes risk, the strength of your immune system, and even your chance of developing depression.

In 2004, University of Chicago researchers restricted a group of men to only 4 hours of sleep per night. After just 2 nights, the men had an 18 percent decrease in leptin, a hormone that tells your brain when you are full, and a 28 percent increase in ghrelin, a hormone that triggers hunger. These results were reinforced last October by a study of almost 10,000 adults that found that people who slept fewer than 7 hours a night were more likely to be obese than those who got 7 hours of shut-eye. "

Chronic sleep deprivation causes changes in metabolism that produce a state that stimulates hunger," Epstein explains. Sleep deprivation can also affect how your body handles insulin; insulin resistance puts you at risk for weight gain and diabetes.

In a study that's still under way, Van Cauter and her colleagues are looking at chronic sleep loss in a group of normal-weight men and women under age 30. Over 6 months, those who slept fewer than 6.5 hours a night were more insulin-resistant than normal sleepers who logged 7.5 to 8 hours per night.

The short sleepers, the study shows so far, need to produce 30 to 40 percent more insulin to dispose of the same amount of glucose. Still other studies suggest that over time, sleep loss may play a role in the development of depression.

"Positive moods are lower in people with sleep loss," Van Cauter says, "and mood isn't stable over the 24-hour cycle. People have lower moods in the morning. They also have higher levels of cortisol, the stress hormone. All those changes are typical of clinical depression."

Whether it's depression, diabetes, or a bigger dress size, the threat posed by sleep deprivation is real. Sleep disorders can be treated, but often patients fail to recognize the problem -- leading to more sleepless nights.

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