The amount of time that a person sits during the day is associated with a higher risk of heart disease, diabetes, cancer, and death, regardless of regular exercise, researchers reported in the January 20 issue of the Annals of Internal Medicine.


David Alter, PhD, MD, and colleagues conducted a meta-analysis of 47 articles that met their eligibility criteria. Significant hazard ratio (HR) associations were found with all-cause mortality (HR, 1.240), cardiovascular disease mortality (HR, 1.179), cardiovascular disease incidence (HR, 1.143), cancer mortality (HR, 1.173), cancer incidence (HR, 1.130), and type 2 diabetes incidence (HR, 1.910). Hazard ratios associated with sedentary time and outcomes were generally more pronounced at lower levels of physical activity than at higher levels.


“More than one half of an average person’s day is spent being sedentary—sitting, watching television, or working at a computer,” said Dr. Alter, Senior Scientist, Toronto Rehabilitation Institute, University Health Network (UHN), and the 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 investigators noted that the negative effects of sitting time on health are more pronounced among those who do little or no exercise than among those who participate in greater amounts of exercise.


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


Dr. Alter outlined strategies that 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 behavior,” he said. “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.”.