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Even for the active, a long sit shortens life and erodes health

Maybe those of us who sit for long hours in meetings, on phone calls, and tapping away at keyboards should be getting hazard pay. New research that distills the findings of 47 studies concludes that those of us who sit for long hours raise our average risk of cancer, cardiovascular disease, type 2 diabetes and early death.

Even for those of us who meet recommended daily levels of exercise, sitting for long periods of time boosts our likelihood of declining health. (In fact, I just worked out intensively for 90 minutes, and am now risking life and limb to bring you this news. You're welcome.)

To be sure, the latest research -- published Monday in the Annals of Internal Medicine -- finds that the risk of poor health "is more pronounced at lower levels of physical activity than at higher levels."

Those who engage in regular physical activity but still spend a large proportion of their day in sedentary activity were found, on average, to be 30% less likely to die of any cause in a given period than were those who get little to no exercise. But even those who punctuate a long day of sitting with a vigorous workout were estimated to be 16% more likely to die of any cause in a given time than were those who do not sit for long.

The studies that formed the basis for such aggregations defined prolonged sitting, as well as high levels of physical activity, quite differently. While one study included participants who spent as little as an hour a day seated, the rest defined prolonged sitting as those who watched television for at least five hours a day on up to those who had more than six and, in one study, more than 11 hours of "sitting time" a day.

Any way you read it, these studies probably sweep most of us into the long-sitting category, since researchers estimate that more than half of the average American's waking life is spent sitting.

The compensating effects of exercise were also measured differently in each study. High levels of physical activity were variously defined as "meeting physical activity guidelines" -- at least 20 minutes a day of moderately vigorous exercise -- to spending at least seven hours a week engaged in moderately vigorous exercise.