Oh please, not the “sex causes heart attack” story again

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Sexual activity nearly triples the risk of having a heart attack, report researchers from Tufts University and the Harvard School of Public Health in yesterday’s Journal of the American Medical Association.

For anyone who is sexually active—especially anyone worried about his or her heart—that’s an eye-catching and fear-inducing finding. It’s a message reinforced by television (Downton Abbey, Mad Men, and Rescue Me are just a few series that have used heart attack after sex as a plot device). But before you swear off sex forever, realize that “triples” refers to the relative risk. It’s calculated like this: A day or two day after having a heart attack, an individual is asked to recount all of the things he or she had done in the hours before the attack. Then as a “control,” the person is asked to list what he or she had done the day before (a day without a heart attack). The various activities on the heart attack day are compared with those on the non-attack day to calculate the relative risk.

But the relative risk isn’t nearly as important as the absolute risk. Here’s a calculation by Dr. James E. Muller, a cardiologist at Harvard-affiliated Massachusetts General Hospital, in an earlier article about sex and heart attack. The absolute risk of heart attack for a 50-year-old man who exercises regularly is 1 chance in a million per hour. Tripling that risk by engaging in sexual activity boosts it to 3 in one million per hour, and only for the two-hour period during and after sexual activity. For a heart attack survivor who is getting back into shape, the absolute risk of 10 in one million per hour increases to 30 in one million per hour.

In other words, sex can trigger a heart attack, but it doesn’t happen very often. What’s more, in the JAMA study the chances of having a sex-related heart attack was lower in people who regularly exercised than it was among those who rarely exercised.

When sex is classified as a form of physical exertion, it’s pretty far down there in the mild to moderate intensity category. Sexual activity averages 2 to 3 metabolic equivalents (METs), a measure of energy expenditure, and may go up to 3 to 4 METs at orgasm. In comparison, walking slowly on level ground or doing light housework clocks in at 2 METs; climbing stairs, 3 to 4 METs; shoveling light snow, 6 to 7 METs.

The numbers for sexual activity are averages, of course. Sexual positions affect the potential effects on the heart. A study published in the Archives of Internal Medicine showed greater energy expenditure during sexual intercourse for both partners with the man on top (2.0 to 5.4 METs) than with the woman on top (2.5 to 3.0 METs). And sex with a new partner in an unfamiliar setting increases the relative risk more than sex with a familiar partner in a familiar setting.

The good news from this study is that sex is a relatively rare trigger of heart attack or sudden death—even less than shoveling snow. The even better news is that regular physical activity, like walking or having sex, reduces the relative risk of having a heart attack while exercising or having sex by five-fold or more, according to the JAMA study. Factor in the fact that regular physical activity improves sexual function, and it’s amazing that walking trails, cycling routes, and other exercise venues aren’t always mobbed.

To learn more about the benefits of exercise, take a look at “Exercise: A program you can live with” a Special Health Report from Harvard Health Publishing. Click here to see the contents and read an excerpt.