Purpose: 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 (ICC1,1).
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 ICC1,1 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 (ICC1,1 = 0.71; 95% CI = 0.66-0.75) and household activities (ICC1,1 = 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.
1Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC; 2Exponent, Menlo Park, CA; and 3Department of Epidemiology, University of Washington, Seattle, WA
Address for correspondence: Anne-Marie Meyer, Ph.D., NC Center for Public Health Preparedness, University of North Carolina at Chapel Hill, CB # 8165, 400 Roberson St., Chapel Hill, NC 27599; E-mail: firstname.lastname@example.org.
Submitted for publication November 2007.
Accepted for publication July 2008.