Sedentary behavior contributes to the risk of cardiovascular disease (CVD) and diabetes, according to a science advisory released by the American Heart Association (AHA).
The AHA’s advisory examines the assessment methods, population prevalence, determinants, associations with CVD incidence and mortality, potential underlying mechanisms, and interventions of sedentary behavior.
Adults spend approximately 6 to 8 hours per day in sedentary behavior, which includes sitting, watching TV, and using the computer. However, the prevalence rate can vary depending on the assessment tool and may be affected by sex and ethnicity.
The investigators note that there is no “gold standard” for sedentary behavior assessment, but self-reported measures can provide behavioral context that cannot be obtained from objective measures. In addition, accelerometers are frequently used to objectively monitor sedentary time by measuring acceleration, and other objective measures to assess body position are also in development.
“There currently is insufficient evidence on which to base specific public health recommendations regarding the appropriate limit to the amount of sedentary behavior required to maximize CVD health benefits,” the study authors concluded. “Given the current state of the science on sedentary behavior and in the absence of sufficient data to recommend quantitative guidelines, it is appropriate to promote the advisory, ‘Sit less, move more.’”
Evidence outlined in the advisory also suggests that psychological well-being is inversely associated with sedentary behavior. Genetics may also contribute to sedentary behavior, although further studies are required to determine specific loci and detect significant effects. The researchers also stated that “multiple genetic variants with small effect sizes are present in the population and could interact with environmental factors to contribute to the overall degree of sedentary behavior in an individual.”
The investigators found that long periods of sedentary behavior can lead to reduced insulin sensitivity, but this can also be prevented with short bursts of physical activity. A meta-analysis conducted by Grøntved et al found that every 2-hour period of TV watching per day was associated with a relative risk of 1.20 of developing type 2 diabetes. Sedentary behavior was associated with an increased risk of type 2 diabetes in both men and women of diverse ethnic backgrounds.
Several meta-analyses have also linked prolonged TV watching to increased CVD events (hazard ratio [HR]: 1.17). In addition, data from the EPIC (European Prospective Investigation Into Cancer and Nutrition) Norfolk study showed that every hour of TV watching per day was associated with an increased risk of total CVD risk (HR: 1.06), nonfatal CVD (HR: 1.06), and coronary heart disease (HR: 1.08).
Intervention strategies that focus only on reducing sedentary activity were more effective than the strategies that sought to increase physical activity in addition to reducing sedentary behaviors. Smartphone applications may also be useful for strategies to interrupt sedentary time, but further studies are required to assess the potential of the technology.
“Risk factors for sedentary behaviors need to be identified,” the study authors wrote. “There is a paucity of prospective data on modifiable risk factors for sedentary behaviors, from personal psychological characteristics to microenvironmental and macroenvironmental factors. Both observational prospective cohort and intervention studies, including randomized trials, are necessary to address these gaps.”
Young DR, Hivert MF, Alhassan S, et al. Sedentary behavior and cardiovascular morbidity and mortality: a science advisory from the American Heart Association. Circulation. 2016; doi: 10.1161/CIR.0000000000000440.