Effect of temporal domain on self-reported walking behaviors in the California Health Interview Survey.

BACKGROUND: Question design can influence the validity and reliability of physical activity (PA) self-report instruments. This study assesses the effect of temporal domain ("days" walked versus "times" walked) on survey questions about walking behavior.
METHODS: A 2005 California Health Interview Survey (CHIS) subsample (n = 6332) reported the number of days or times they walked for leisure or transportation in the past 7 days and the usual time spent per day or per time. Question order was randomized by temporal domain. Minutes walked per week (mean ± SE) and adherence to PA guidelines (≥150 min/wk) were assessed.
RESULTS: Estimates of leisure walking remained stable across temporal domain (days = 71.4 ± 2.5 min; times = 73.4 ± 2.4 min), but transportation walking differed depending on domain (days = 70.4 ± 3.2 min; times = 52.5 ± 2.6 min). Adherence to PA guidelines based on leisure walking was stable across temporal domain (days = 14.9 ± 0.6%; times = 14.9 ± 0.6%), but again differed by domain for transportation walking (days = 10.4 ± 0.6%; times = 7.8 ± 0.5%). A large order effect (number-of-days versus number-of-times asked first) was observed for reports of days walking for transportation (days first = 87.8 ± 2.9 min; times first = 52.3 ± 2.5 min).
CONCLUSION: Temporal domain influences estimates of self-reported transportation walking behavior. Current efforts to capture PA from both transportation and leisure activities in health research appear to present distinct methodological challenges.