title: Bidirectional association between mental health and physical activity in older adults: Whitehall II prospective cohort study.
abstract: OBJECTIVE
  To investigate longitudinal and bidirectional associations between mental health and physical activity from midlife into old age.
  
  
  METHODS
  Analysis was based on data from 6909 participants (aged 45 to 69 in 1997/99) from the Whitehall II cohort in the UK. Latent growth curve analysis examined possible bidirectional associations between the SF-36 Mental Component Summary and weekly physical activity measured at three time-points over ten years.
  
  
  RESULTS
  Mental health and physical activity were associated at baseline (β=0.17, 95% CI 0.13, 0.21) and associations persisted into old age. In the latent growth curve model, both mental health and physical activity increased and their rates of change 'moved together' over time (β=0.24, 95% CI 0.11, 0.37). Relatively high baseline levels of either variable were associated with slightly slower increases in the other outcome (β=-0.02, 95% CI -0.03, -0.01; β=-0.07, 95% CI -0.11, -0.13), which are thought to reflect regression to the mean. However, those who started high on either variable remained the most advantaged at end of follow-up.
  
  
  CONCLUSIONS
  From midlife to old age, greater physical activity is associated with better mental health and vice versa. These findings suggest persistent longitudinal and bidirectional associations between physical activity and mental health.
authors.affiliation: Department of Clinical, Education and Health Psychology, University College, London, UK. Electronic address: s.steinmo.11@ucl.ac.uk.
authors.forename: Siri
authors.initials: S
authors.lastname: Steinmo
authors.affiliation: Department of Epidemiology and Public Health and Institute of Child Health, University College, London, UK.
authors.forename: Gareth
authors.initials: G
authors.lastname: Hagger-Johnson
authors.affiliation: Department of Epidemiology and Public Health, University College, London, UK.
authors.forename: Lion
authors.initials: L
authors.lastname: Shahab
mesh_terms: D000368:Aged; D015444:Exercise / Q000523:psychology*; D005260:Female; D006801:Humans; D008297:Male; D008603:Mental Health; D008875:Middle Aged; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D006113:United Kingdom
keywords: Aging; Bidirectional associations; Latent growth curve models; Longitudinal study; Mental health; Older adults; Physical activity; SF-36 Mental Component Summary