Among 7,000 older women who wore an accelerometer to measure their movement, about two-thirds of their waking time was spent in sedentary behavior, most of which occurred in periods of less than 30 minutes, according to a study appearing in the December 18 issue of JAMA. Recent studies suggest sedentary behavior may be a risk factor for adverse health outcomes. However, few data exist on how this behavior is patterned (e.g., does most sedentary behavior occur in a few long periods or in many short periods), according to background information in the article.
Eric J. Shiroma, M.Ed., M.S., of the Harvard School of Public Health, Boston, and colleagues examined details of sedentary behavior among 7,247 older women (average age, 71 years) who were asked to wear an accelerometer for 7 days during waking hours. Women wore the accelerometer for an average of 14.8 hours per day. The average percentage of wear time spent in sedentary behavior was 65.5 percent, equivalent to an average of 9.7 hours per day.
Total sedentary time increased and the number of periods of sedentary behavior and breaks per sedentary hour decreased as age and body mass index increased. Most sedentary time occurred in periods of shorter duration. Among the total number of sedentary bouts, the average percentage of bouts of at least 30 minutes was 4.8 percent, representing 31.5 percent of total sedentary time.
"If future studies confirm the health hazards of sedentary behavior and guidelines are warranted, these data may be useful to inform recommendations on how to improve such behavior," the authors conclude.