Screen-based sedentary behavior, physical activity, and muscle strength in the English longitudinal study of ageing. PloS One 2013; 8: e66222

Background: Sarcopenia is associated with loss of independence and ill-health in the elderly although the causes remain poorly understood. We examined the association between two screen-based leisure time sedentary activities (daily TV viewing time and internet use) and muscle strength. Methods and Results: We studied 6228 men and women (aged 64.969.1 yrs) from wave 4 (2008-09) of the English Longitudinal Study of Ageing, a prospective study of community dwelling older adults. Muscle strength was assessed by a hand grip test and the time required to complete five chair rises. TV viewing and internet usage were inversely associated with one another. Participants viewing TV $6hrs/d had lower grip strength (Men, B =21.20 kg, 95 % CI, 22.26, 20.14; Women, 20.75 kg, 95 % CI, 21.48, 20.03) in comparison to,2hrs/d TV, after adjustment for age, physical activity, smoking, alcohol, chronic disease, disability, depressive symptoms, social status, and body mass index. In contrast, internet use was associated with higher grip strength (Men, B = 2.43 kg, 95 % CI, 1.74, 3.12; Women, 0.76 kg, 95 % CI, 0.32, 1.20). These associations persisted after mutual adjustment for both types of sedentary behaviour. Conclusions: In older adults, the association between sedentary activities and physical function is context specific (T