“Many adults in sedentary occupations spend more time sitting at work than they spend sitting in their leisure time,” said lead review author Jannique van Uffelen, Ph.D. “Sitting at work could affect health and for some people, current levels of leisure time physical activity may not be enough to offset these effects.”
Van Uffelen, a research fellow with the University of Queensland in Australia, and colleagues examined 43 studies that tracked sedentary time at work for more than 2 million employees.
Researchers examined the association of occupational inactivity’s with body mass index (BMI), cancer, heart disease, diabetes and mortality. They used both cross-sectional studies (performed at one time) and prospective studies (which follow participants over time)
The review appears online and in the October issue of the American Journal of Preventive Medicine.
Jeffrey Harris, M.D., director of the University of Washington Health Promotion Research Center in Seattle, said that although the review was done carefully, the results do not paint a clear picture.
“Is it worth it for people to move from sitting to light activity at work? The answer out of the review is: We’re not sure,” Harris said. He was not affiliated with the review.
Van Uffelen noted that the authors expected to find studies linking sitting and obesity, since inactivity results in fewer calories burned. But only half of the cross-sectional studies found a higher BMI in inactive workers, and prospective studies did not confirm this finding at all, she said.
In other words, sitting does not necessarily cause high BMI or weight. It could be that people who have a high BMI sit more, van Uffelen said.
Four of six studies found an increased risk of death for sedentary workers, indicating a long-term health risk. Three of four studies also linked occupational sitting to a higher risk of diabetes, but there was no evidence sitting at work causes cancer or cardiovascular disease, the authors reported.
“We really do not know enough about this yet to be able to define how much sitting is too much, and if decreasing sitting time is associated with better health,” van Uffelen said.
“We are quite sure that moderate and vigorous activity are good for you and will reduce your risk of heart disease and your risk of death,” Harris said. “What is clear is that we need to move 30 minutes a day, whether that’s at work or at home.”
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American Journal of Preventive Medicine: Contact the editorial office at (858) 534-9340 or eAJPM@ucsd.edu.
van Uffelen JGZ, et al. Occupational sitting and health risks: a systematic review. Am J Prev Med 39(4), 2010.