Dear HEALTHbeat subscriber,

In our May 12th issue, we let you know about some healthful habits that are also, well, enjoyable! (And you thought the two were mutually exclusive.) This week we complete our series by letting you know how sleep, socializing, and sex can benefit your health. Also in this issue, Dr. Anthony L. Komaroff, editor in chief of the Harvard Health Letter, discusses how much is the “right amount” of sleep.

Wishing you good health,


Nancy Ferrari
Managing Editor
Harvard Health Publications
HEALTHbeat@hms.harvard.edu

Sex

Obviously a satisfying sex life is a source of pleasure and contributes to a sense of well-being, but even after the immediate glow fades, there may be residual health benefits.

It is very rare that sexual activity can cause heart attacks, and in fact, some research suggests that frequent sexual intercourse (twice a week) is associated with reduced heart attack risk, even after making the statistical adjustments necessary to account for the fact that men who have sex that often are healthier over all.

Exercise for your sex life?

Even if sex isn’t great aerobic exercise, exercise may make for better sex: several studies have shown that moderate exercise increases genital response to erotic stimuli in women.

The fact is that much of the research into health and sexual activity has focused on how illness adversely affects sexuality, a worthy topic, but it might be revealing to turn the tables and pay a little more attention to the vice versa: how sexual activity may have ameliorating effects on illness.

Sleep

We’re resting easier (sometimes longer) these days because of the laurels that sleep is winning for its health benefits — or, more precisely, because of the evidence of all the bad things that can happen when we don’t get enough of it. Several studies have shown that “short sleepers” put on more pounds than people who sleep seven to eight hours a night—the amount of sleep that seems optimal for most adults.

Other studies have linked skimping on sleep to the high-risk pool for heart attacks, diabetes, and early death. The risks are more pronounced for people who sleep less than five hours a night, but the danger seems to extend to those averaging less than six. And of course, lack of sleep has a very direct effect on the brain, influencing memory, mood, and attention.

Can you sleep too much?

Several of the epidemiologic studies of sleep show that long sleep (nine hours nightly or more) is associated with just as many health problems as short sleep, if not more. But it’s probably more often the case that an underlying illness (depression is a prime example) causes people to sleep more, not the other way around.

Social life

We could all use a little help from our friends, but just having them may also help us stay healthier. A slew of studies has shown an association between social networks and good health. Cognitive decline, high blood pressure, the risk of dying after a heart attack — they’ve all been linked to social isolation and loneliness.

Sorting out cause and effect is difficult. Ill-health itself can strain social ties, although it’s also true that coworkers, friends, and relatives tend to rally around people who have strong social networks prior to getting ill. Tending to friendships, family, and community life is a good habit to cultivate for health and other reasons.

Q: I heard about a study that found people who sleep six and a half to seven hours a night will live longer than those sleeping eight to nine. What is the right amount of sleep?

A. You’re asking an important question, but it’s hard to answer, and here’s why:

Consider the perfect study to answer the question. First, you would recruit a large number of people — say, about 100,000. Then you’d randomly assign some of them to sleep five hours a night, others six, others eight, and so on. You’d also have to figure out some way to make sure people stick with their assigned sleep amounts. Then you’d carefully monitor the health of the study participants — for decades.

You can see how impractical such a perfect study would be. So what we have instead are observational studies that, after following people for many years, find statistical associations between habits and health outcomes. A number of these studies have asked the participants about their sleeping habits. Not all of the results agree, but most suggest that the farther away you get from the “sweet spot” of six to eight hours a night, the greater the risk of death.

But observational studies can’t prove causality, so they can’t show, for example, that changing from five hours of sleep a night to six or seven for the next 20 years will help you live longer. An excellent study from the University of Pennsylvania found that people who sleep less than eight hours a night have lower cognitive performance than people who sleep eight hours or more. If that’s true, maybe you should sleep eight and a half hours nightly if your goal is to be clearheaded, but six to seven if your goal is longevity!

What do I do? As a rule, I sleep seven hours weeknights and eight hours on weekends, because those are the amounts I need to feel best. All of the studies I’ve talked about give “on average” answers. However, we’re all different, and some people need more sleep than others. I think you can figure out what your personal sleep requirements are by listening to the wisdom of your body.

— Anthony L. Komaroff, M.D.
Editor in Chief, Harvard Health Letter

This Question and Answer first appeared in the November 2008 Harvard Health Letter, available at www.health.harvard.edu/health.