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Validity of Two Self-Report Measures of Sitting Time
- Added on June 16, 2011
Introduction Evidence suggests that time spent in sedentary behaviours (usually defined as time spent sitting) is an independent risk factor for a number of adverse health outcomes  and there have been calls for the explicit measurement of sedentary behaviour in population surveillance studies . To date, limited evidence exists on the validity of self-reported measures of sedentary behaviour. This study examined the criterion validity of two different self-report measures of sitting time.
Methods 44 healthy volunteers (30% male, age = 41.5±12.8 years, BMI = 24.8±4.7 kg/m2) wore an ActiGraph accelerometer (the criterion measure) for seven consecutive days. During each day of monitoring, participants recorded their daily sitting time by responding to the single-item question “how long have you been sitting for today?” in a daily diary. Participants completed this specific-day question on a daily basis just before going to bed each night. After seven days, participants completed a new domain-specific sitting time questionnaire that requires participants to retrospectively report sitting times in different domains (i.e. time spent sitting whilst travelling to and from places, at work, watching TV, using a computer at home, and during leisure time), on a usual weekday and weekend-day . Total sitting times recorded from the single-item question and from the domain-specific questionnaire were compared with mean accelerometer-determined sedentary time (minutes/day of <100 counts/minute) for weekdays and weekend-days.
Results Accelerometer-determined sedentary times (mean ± SD) for weekdays and weekend-days were 639.7±133.9 and 612.4±132.7 minutes respectively. Total sitting time calculated from the domain-specific questionnaire did not differ significantly from accelerometer-determined sedentary time on either weekdays (mean difference = -13.7 minutes [95% CI = -69.2 to 41.8]) or weekend-days (-4.2 minutes [95% CI = -91.7 to 83.4]). Sitting time was significantly underestimated using the single-item specific-day question on weekdays (-173 minutes [95% CI = -207.5 to -138.5]) and weekend-days (-219 minutes [95% CI = -262.9 to -174.2]). From the domain-specific questionnaire, the greatest contributor to daily sitting time was sitting at work on weekdays and watching TV on weekends.
Discussion and Conclusion When assessed via self-report, the estimation of total sitting time is improved by summing sitting times reported across different domains. Estimates of sitting time are more precise for weekdays than for weekend-days. The continued improvement of self-report measures of sitting time, particularly for weekend-days, will be important if we are to further our understanding of the links between sedentary behaviour and health.
References  Katzmarzyk PT, Church TS, Craig CL, Bouchard C. Sitting time and mortality from all causes, cardiovascular disease, and cancer. Med Sci Sports Exerc, 2009; 41: 998- 1005.  Owen N, Leslie E, Salmon J, Fotheringham MJ. Environmental determinants of physical activity and sedentary behavior. Exerc Sport Sci Rev, 2000; 28: 153-8.  Marshall AL, Miller YD, Burton NW, Brown WJ. Measuring total and domain-specific sitting: a study of reliability and validity. Med Sci Sports Exerc, 2010; 42: 1094-102.
ICAMPAM- Glasgow 2011