Validity of Two Self-Report Measures of Sitting Time

Background: in light of evidence linking sedentary behaviors to health outcomes, there have been calls for the measurement of sedentary behavior in surveillance studies. This study examined the convergent validity of 2 self-report measures of sitting time and accelerometer-determined sedentary time (minutes/day of <100 counts/minute). Methods: 44 adults wore an ActiGraph accelerometer for 7 days, during which they also recorded daily sitting time in a diary, in response to a single-item question. After 7 days, participants completed a new domain-specific questionnaire to assess usual weekday and weekend-day sitting time. Total sitting times recorded from the self-report measures were compared with accelerometer-determined sedentary time. Results: Total sitting time calculated from the domain-specific questionnaire did not differ significantly from accelerometer-determined sedentary time on weekdays (mean difference [+/- SE] = -14 +/- 28 mins/day) and weekend days (-4 +/- 45 mins/day, both P > .05). Sitting time was significantly underestimated using the single-item specific-day question on weekdays (-173 +/- 18 mins/day) and weekend days (-219 +/- 23 mins/day, both P < .001). Conclusions: When assessed via self-report, the estimation of total sitting time is improved by summing sitting times reported across different domains. The continued improvement of self-report measures of sitting time will be important if we are to further our understanding of the links between sedentary behavior and health.