Sitting worse than you think?

NPR is pretty exercised about a study showing greater risk of death by cardiovascular disease if you sit for extended periods of time.

Men who reported more than 23 hours a week of sedentary activity had a 64 percent greater risk of dying from heart disease than those who reported less than 11 hours a week of sedentary activity. And many of these man routinely exercised.

Big scary numbers, at least until you look at the study.

Out of a pool of 7,744 participants, 377 died of heart disease. Of those, 92 were classified by the study as “physically inactive.” The number of fatalities in the sit-all-day category: 19.2.

In other words, 0.24% of the sample population both died from cardiovascular heart disease and were sedentary for much of the day.

Other things to notice about the study: participants reported on their own activity levels on a questionnaire once in 1982 — the methodology statement says nothing about followup studies. In the intervening 21 years their levels of activity could have changed greatly. There is also this, which suggests the sample was not particularly random nor well-distributed across cultural groups:

Participants were self-referred or employer referred to the clinic for various services such as preventive medical examinations and health, nutrition, and exercise counseling. Most participants were Caucasian from middle or upper socioeconomic strata.

That doesn’t mean sitting isn’t bad for you; but I’m not leaping up from my desk every hour to march in place for ten minutes based on this evidence.