Ask Dr. K: Study on TV’s health effects not conclusive

Actually, it may. My colleague Dr. Robert Shmerling is an associate professor of medicine at Harvard Medical School. He noted that a recent study shows watching a lot of TV is worse for your health than other activities that involve long periods of sitting.

The study Dr. Shmerling referred to enrolled more than 13,000 young and middle-aged adults. Researchers asked the study subjects how much time they spent watching TV, using a computer and driving.

During the study:

— People who reported watching three or more hours of TV each day had twice the risk of death as those who watched less than an hour each day.

— People who spent the most time driving or using a computer did not have higher rates of death than people who spent less time at these activities.

This study only showed a link between TV and early death. It was not designed to prove whether watching TV actually caused the higher risk of death. People who watch a lot of TV might also do a lot of other things that put their health at risk. They might be under a lot more stress, and TV might be an escape. They might be having trouble sleeping, or are sleep-deprived, and watching TV to try to go to sleep.

And what were the people eating while they watched TV? The study did not say. Three or more hours a day of eating a lot of cheese and nachos might not be the best thing for your health, regardless of what you were doing while you ate.

There were other limitations to this study. For example, people were asked about their activities only once, yet the study lasted years. The study participants’ activity level could have changed dramatically over the years of the study.

What’s more, this study looked at the impact of physical activity, body mass index and smoking on early death. But it did not take into account other factors (like blood pressure) that could have affected the results.

So I’m not convinced that watching TV is itself hazardous to your health. To put it simply, I don’t plan to cut back on the time I spend with my shows! But just as there are some foods full of empty calories, there are some programs that are “empty TV.” There’s no doubt that substituting physical activity for empty TV would be good for your health.

Thirty minutes of moderate-intensity aerobic exercise most days of the week, plus some muscle-strengthening exercises, will get you further down the road to good health than even the most heart-pounding TV drama.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.