After examining the data, they found that most people sat for 77 percent of their waking hours, the equivalent of 12 hours, and after a four-year follow-up, 340 of the subjects had died.
Those with the greatest amount of sedentary time of 13 hours per day, who sat for 60-90 consecutive minutes at a time, had a two-fold increase in death risk, compared to those who sat for less time. Those who had 30-minute sitting bouts had a lower risk for early death.
"This study adds to the growing literature on how dangerous long periods of sitting are for our health and underscores a growing awareness among clinicians and researchers that sitting really is the new smoking," co-author Monika Safford said in a statement. "We need creative ways to ensure that we not only cut back on the total amount we sit, but also increase regular interruptions to sitting with bursts of activity."
While their findings, which were published in the Annals of Internal Medicine, did not reveal how much activity is optimal to reduce early death risk, they recommend moving around as much as possible.
"So if you have a job or lifestyle where you have to sit for prolonged periods of time, we suggest taking a movement break every half hour," co-author Keith Diaz said.