title: Test-retest reliability of the Women's Health Initiative physical activity questionnaire.
abstract: OBJECTIVE
  Few physical activity (PA) questionnaires were designed to measure the lifestyles and activities of women. We sought to examine the test-retest reliability of a PA questionnaire used in the Women's Health Initiative (WHI) study. Differences in reliability were also explored by important covariates.
  
  
  METHODS
  Participants (n = 1092) were postmenopausal women aged 50-79 yr, randomly selected from the baseline sample of participants in the WHI Observational Study. The WHI PA questionnaire collects usual frequency, duration, and pace of recreational walking, frequency, and duration of other recreational activities or exercises (mild, moderate, and strenuous), household, and yard activities. Approximately half of the women (n = 569) repeated questions on recreational PA, the other half (n = 523) repeated questions related to household and yard activities (mean 3 months apart). Test-retest reliability was assessed with kappa and intraclass correlation coefficients (ICC 1,1).
  
  
  RESULTS
  Overall, questions on recreational walking, moderate recreational PA, and strenuous recreational PA had higher test-retest reliability (weighted kappa range = 0.50-0.60) than questions on mild recreational PA (weighted kappa range = 0.35-0.50). The ICC 1,1 for moderate to strenuous recreational PA was 0.77 (95% confidence interval [CI] = 0.73-0.80), and the total recreational PA was 0.76 (95% CI = 0.71-0.79). Substantial reliability was observed for the summary measures of yard activities (ICC 1,1 = 0.71; 95% CI = 0.66-0.75) and household activities (ICC 1,1 = 0.60, 95% CI = 0.55-0.66). No meaningful differences were observed by race/ethnicity, age, time between test and retest, and amount of reported PA.
  
  
  CONCLUSIONS
  The WHI PA questionnaire demonstrated moderate to substantial test-retest reliability in a diverse sample of postmenopausal women.
authors.affiliation: Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. meyera@email.unc.edu
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Meyer
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Evenson
authors.forename: Libby
authors.initials: L
authors.lastname: Morimoto
authors.forename: David
authors.initials: D
authors.lastname: Siscovick
authors.forename: Emily
authors.initials: E
authors.lastname: White
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D005260:Female; D006801:Humans; D008019:Life Style; D008875:Middle Aged; D009043:Motor Activity; D017698:Postmenopause; D044469:Racial Groups / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D014481:United States