title: The influence of long-term exposure and timing of physical activity on new joint pain and stiffness in mid-age women.
abstract: OBJECTIVE
  To examine the influence of long-term exposure and timing of physical activity (PA) on new joint pain/stiffness in mid-age women.
  
  
  METHODS
  Data were from 5105 participants (born 1946-51) in the Australian Longitudinal Study on Women's Health (ALSWH) who completed survey items on PA (1998, 2001 and 2004) and joint pain/stiffness (2007 and 2010). PA was categorized in five levels at each survey and summed into a cumulative PA score (CPA, range 0-12). Associations were analysed using logistic regression, with separate models for the cumulative model (using CPA), the sensitive periods model (i.e., PA measured at each survey in one regression model) and the critical periods model (i.e., separate regression models for PA at each survey).
  
  
  RESULTS
  951 (18.6%) participants reported new-onset joint pain/stiffness. In the cumulative model, CPA was associated joint pain/stiffness when included as a continuous variable (adjusted odds ratio [OR] = 0.97, 95% confidence interval [CI] = 0.95-0.99), but not when included as a categorical variable. In both the sensitive periods and critical periods models, low to high levels of PA in 2001 and 2004 had stronger inverse associations with joint pain/stiffness than PA levels in 1998. The model fit was better for the sensitive periods than the cumulative or critical periods models.
  
  
  CONCLUSIONS
  In mid-age women, PA between the ages 47 and 58 was associated with a lower risk of joint pain/stiffness 9 years later. Associations were stronger for PA in the last 6 years than for earlier PA.
authors.affiliation: The University of Queensland, School of Human Movement Studies, Brisbane, Australia; The University of Queensland, School of Population Health, Brisbane, Australia. Electronic address: g.peeters@uq.edu.au.
authors.forename: G M E E Geeske
authors.initials: GM
authors.lastname: Peeters
authors.affiliation: Physical Therapy Research, Program in Clinical Health Sciences, University Medical Center Utrecht, Utrecht, The Netherlands; Department of Rehabilitation, Nursing Science and Sport, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands. Electronic address: m.f.pisters@umcutrecht.nl.
authors.forename: M F
authors.initials: MF
authors.lastname: Pisters
authors.affiliation: The University of Queensland, School of Population Health, Brisbane, Australia. Electronic address: g.mishra@uq.edu.au.
authors.forename: G D
authors.initials: GD
authors.lastname: Mishra
authors.affiliation: The University of Queensland, School of Human Movement Studies, Brisbane, Australia. Electronic address: wbrown@hms.uq.edu.au.
authors.forename: W J
authors.initials: WJ
authors.lastname: Brown
mesh_terms: D000367:Age Factors; D000368:Aged; D018771:Arthralgia / Q000453:epidemiology* / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000453:epidemiology / Q000517:prevention & control; D008137:Longitudinal Studies; D008875:Middle Aged; D009043:Motor Activity; D011795:Surveys and Questionnaires; D013997:Time Factors
keywords: Exercise; Life-course modelling; Osteoarthritis