Prolonged sitting time is a well-established health risk factor

Prolonged sitting time is a well-established health risk factor. Already in the 50’s a 2-fold risk of myocardial infarction has been demonstrated in London bus drivers compared to active bus conductors. However, as previous conclusions from reviews of sedentary behavior and health outcomes in adults beyond just TV viewing times were based on a small number of studies and did not allow for a meta-analysis, the aim of the present systematic review and meta-analysis was to quantitatively synthesize observational evidence relating sitting time to 1) diabetes, 2) cardiovascular (CV) disease, 4) CV mortality and all-cause mortality. 

4,835 articles were identified. Due to strict inclusion criteria using measures of time spent in sedentary behaviors and not defining sedentary behavior as an absence of moderate-to-vigorous physical activity (MVPA), 18 studies remained (16 prospective, 2 cross-sectional, included 794,577 participants). Higher levels of sedentary time were associated with a significantly increased risk of diabetes (+112%), CV disease (+147%), CV mortality (+90%) and all-cause mortality (+49%). 

The reported associations between sedentary time and clinical outcomes were largely independent of physical activity, indicating that deleterious effects of prolonged sitting are not mediated through lower amounts of MVPA. In this context evidence emerged that interrupting prolonged sitting with 2-min bouts of light activity every 20 min reduces postprandial glucose and insulin levels in overweight/obese adults by 23% and 24%, respectively. > From: Wilmot et al., Diabetologia 55 (2012) 2895-2905. All rights reserved to Springer-Verlag.