title: Associations of changes in exercise level with subsequent disability among seniors: a 16-year longitudinal study.
abstract: BACKGROUND
  The effect of changes in physical exercise on progression of musculoskeletal disability in seniors has rarely been studied.
  
  
  METHODS
  We studied a prospective cohort annually from 1984 to 2000 using the Health Assessment Questionnaire Disability Index (HAQ-DI). The cohort included 549 participants, 73% men, with average end-of-study age of 74 years. At baseline and at the end of the study, participants were classified as "High" or "Low" vigorous exercisers using a cut-point of 60 min/wk. Four groups were formed: "Sedentary" (Low-->Low; N = 71), "Exercise Increasers" (Low-->High; N = 27), "Exercise Decreasers" (High-->Low; N = 73), and "Exercisers" (High-->High; N = 378). The primary dependent variable was change in HAQ-DI score (scored 0-3) from 1984 to 2000. Multivariate statistical adjustments using analysis of covariance included age, gender, and changes in three risk factors, body mass index, smoking status, and number of comorbid conditions. Participants also prospectively provided reasons for exercise changes.
  
  
  RESULTS
  At baseline, Sedentary and Increasers averaged little exercise (16 and 22 exercise min/wk), whereas Exercisers and Decreasers averaged over 10 times more (285 and 212 exercise min/wk; p <.001). All groups had low initial HAQ-DI scores, ranging from 0.03 to 0.08. Increasers and Exercisers achieved the smallest increments in HAQ-DI score (0.17 and 0.11) over 16 years, whereas Decreasers and Sedentary fared more poorly (increments 0.27 and 0.37). Changes in HAQ-DI score for Increasers compared to Sedentary were significantly more favorable (p <.05) even after multivariate statistical adjustment.
  
  
  CONCLUSIONS
  Inactive participants who increased exercise achieved excellent end-of-study values with increments in disability similar to those participants who were more active throughout. These results suggest a beneficial effect of exercise, even when begun later in life, on postponement of disability.
authors.affiliation: Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305-5755, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Berk
authors.forename: Helen B
authors.initials: HB
authors.lastname: Hubert
authors.forename: James F
authors.initials: JF
authors.lastname: Fries
mesh_terms: D000368:Aged; D006233:Persons with Disabilities; D018450:Disease Progression; D015444:Exercise; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009140:Musculoskeletal Diseases / Q000517:prevention & control*; D011446:Prospective Studies; D013997:Time Factors