Associations between sedentary behaviour and body composition, muscle function and sarcopenia in community-dwelling older adults.

While previous studies have reported detrimental associations of sedentary behaviours with cardiometabolic disorders and mortality, in this study, we report that higher levels of sitting time were associated with a greater risk of sarcopenia, with increased television (TV) viewing negatively associated with lean mass, independent of physical activity. Sedentary behaviour has been linked to cardiometabolic disorders and mortality, but little is known about its effects on musculoskeletal health and function. This study investigated the relationship between total sitting and TV viewing time on sarcopenia and its determinants (muscle mass, strength and function) in older adults. This cross-sectional study included 162 community-dwelling men and women aged 60 to 86 years who had complete assessment of total body and regional lean mass (LM) and fat mass (dual-energy X-ray absorptiometry (DXA)), lower limb muscle strength, power and functional performance. Sarcopenia was defined as the lowest sex-specific quartile for relative appendicular LM plus muscle strength and/or gait speed. Total sitting and TV viewing time were self-reported using a validated questionnaire. A sitting fragmentation ratio, as an index of breaks in sitting time, was calculated as the number of sitting bouts divided by total sitting time. Greater overall sitting time was associated with an increased risk of sarcopenia; for each 1-h increment, the risk increased by 33% [odds ratio 1.33 (95% confidence interval (CI) 1.05, 1.68)], independent of physical activity and other lifestyle and confounding factors. TV viewing time was associated with lower total body and leg LM after adjusting for various confounders and fat mass. There were no associations between total sitting or TV viewing time or the fragmentation ratio with any other measure. Higher levels of sedentary behaviour in older adults were associated with reduced muscle mass and an increased risk of sarcopenia in community-dwelling older adults, independent of physical activity.