It is widely accepted that physical inactivity leads to weight gain, cardiovascular disease and diabetes. New 
research links a sedentary lifestyle to certain cancers, specifically colon, lung and endometrial cancer, according to a study published June 16 in the JNCI: Journal of the National Cancer Institute. The research is significance as it shows sedentary behavior is emerging as an independent risk factor for cancer, chronic disease and mortality. However in a clinical setting, guidelines to improve activity levels for adult patients are poorly defined and difficult to implement.
When the highest levels of sedentary behavior were compared to the lowest, the researchers found a statistically significantly higher risk for three types of cancer—colon, endometrial, and lung. Moreover, the risk increased with each 2-hour increase in sitting time, 8% for colon cancer, 10% for endometrial cancer, and 6% for lung cancer, although the last was borderline statistically significant. The effect also seemed to be independent of physical activity, suggesting that large amounts of time spent sitting can still be detrimental to those who are otherwise physically active. TV viewing time showed the strongest relationship with colon and endometrial cancer, possibly, the authors write, because TV watching is often associated with drinking sweetened beverages, and eating junk foods.
To assess the relationship between TV viewing time, recreational sitting time, occupational sitting time, and total sitting time with the risk of various cancers, Daniela Schmid, Ph.D., M.Sc., and Michael F. Leitzmann, M.D., Dr.P.H., of the Department of Epidemiology and Preventive Medicine, University of Regensburg, Germany, conducted a meta-analysis of 43 observational studies, including over 4 million individuals and 68,936 cancer cases. Data in the individual studies had been obtained with self-administered questionnaires and through interviews.
In a commentary, Lin Yang and Graham A. Colditz, M.D., Dr.P.H., of the Siteman Cancer Center and Department of Surgery, Washington University School of Medicine, St. Louis MO, write:
“Interventions targeting sedentary behaviors in adults are scarce, despite the association of sitting with mortality being independent of physical activity (30). Settings for interventions could vary. For example, given that working adults can spend eight or more hours a day at work, the worksite is an ideal and key setting to reduce sedentary time through worksite policies or changes to the physical work environment (31,32). Such changes require a joint effort between public health, architecture, built environment, occupational, and behavioral science researchers to understand how office layout may influence employees’ activity patterns to guide the development of effective intervention (33).”
“Transportation offers another intervention target. Replacing sedentary time in transport with active commuting may require infrastructure improvement (34) and targeted behavior change program (35). More important, environmental modification and reforming social norms (ie, active transport culture) (36) may shift the overall distribution of sedentary behavior as one means to impact cancer prevention and broader health outcomes at a population level (37).”
Yang and Colditz also say that “strategies remain poorly defined to meet this goal independent of weight control. Priority should be placed on refining interventions, independent of physical activity and obesity prevention, to reduce sedentary time and lower cancer risk and overall mortality. These will then be integrated into a broader framework for an effective strategy to implement and monitor them to reduce the cancer burden as society continues to remove activity from how we structure our civilization.”
SOURCE: An Active Lifestyle for Cancer Prevention
Television Viewing and Time Spent Sedentary in Relation to Cancer Risk: A Meta-analysis
