title: Screen-based sedentary behavior, physical activity, and muscle strength in the English longitudinal study of ageing.
abstract: 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.
  
  
  RESULTS
  We studied 6228 men and women (aged 64.9 ± 9.1 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 ≥ 6 hrs/d had lower grip strength (Men, B = -1.20 kg, 95% CI, -2.26, -0.14; Women, -0.75 kg, 95% CI, -1.48, -0.03) in comparison to <2 hrs/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 (TV viewing vs. computer use). Adverse effects of TV viewing might reflect the prolonged sedentary nature of this behavior.
authors.affiliation: Population Health Domain Physical Activity Research Group, University College London, London, United Kingdom. m.hamer@ucl.ac.uk
authors.forename: Mark
authors.initials: M
authors.lastname: Hamer
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Stamatakis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D015444:Exercise / Q000502:physiology* / Q000523:psychology; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D020407:Internet / Q000706:statistics & numerical data; D007899:Leisure Activities / Q000523:psychology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D057185:Sedentary Behavior; D013690:Television / Q000706:statistics & numerical data; D006113:United Kingdom