The amount of time a person sits during the day is associated with a higher risk of heart disease, diabetes, cancer, and death, regardless of regular exercise, according to a review study published today in the Annals of Internal Medicine.

"More than one half of an average person's day is spent being sedentary -- sitting, watching television, or working at a computer," said Dr. David Alter, Senior Scientist, Toronto Rehab, University Health Network (UHN), and Institute for Clinical Evaluative Sciences. "Our study finds that despite the health-enhancing benefits of physical activity, this alone may not be enough to reduce the risk for disease."

The meta-analysis study reviewed studies focused on sedentary behaviour. The lead author is Avi Biswas, PhD candidate, Toronto Rehab, UHN and the Institute of Health Policy, Management and Evaluation, University of Toronto, and the senior author is Dr. Alter, who is also Associate Professor of Medicine, University of Toronto.

The authors found the negative effects of sitting time on health, however, are more pronounced among those who do little or no exercise than among those who participate in higher amounts of exercise.

"The findings suggest that the health risk of sitting too much is less pronounced when physical activity is increased," said Biswas. "We need further research to better understand how much physical activity is needed to offset the health risks associated with long sedentary time and optimize our health."

Future research will help determine what interventions, in addition to physical activity, are effective against the health risk of sedentary time.

"Avoiding sedentary time and getting regular exercise are both important for improving your health and survival," said Dr. Alter. "It is not good enough to exercise for 30 minutes a day and be sedentary for 23 and half hours."

In the interim, Dr. Alter underlines strategies people can use to reduce sitting time. The target is to decrease sedentary time by two to three hours in a 12-hour day.

"The first step is to monitor sitting times -- once we start counting, we're more likely to change our behaviour," said Dr. Alter. "Next is setting achievable goals and finding opportunities to incorporate greater physical activity -- and less time sitting -- into your daily life. For example, at work, stand up or move for one to three minutes every half hour; and when watching television, stand or exercise during commercials."

Dr. Alter's work is supported by a career-investigator award with the Heart and Stroke Foundation, Ontario Provincial Office; and a Research Chair in Cardiovascular Prevention and Metabolic Rehabilitation at Toronto Rehab, UHN.