Measuring Sitting and Standing at Work Separately: Validating the Brief Occupational Sitting and Physical Activity Questionnaire (OSPAQ)

Introduction Sitting at work is an emerging occupational health risk [1]. Few instruments designed for use in population-based research measure occupational sitting and standing as distinct behaviours [2]. The aim of this study was to develop and validate a brief measure of occupational sitting and physical activity.

Methods A convenience sample (N=99, 61% female) was recruited from two medium-sized workplaces and by word-of-mouth in Sydney, Australia. Participants completed the Occupational Sitting and Physical Activity Questionnaire (OSPAQ) on two occasions, one week apart. On each test occasion, participants reported the time they spent sitting, standing, walking and doing physically demanding tasks at work (OMS-percent, proportion of workday; and OMS-min, minutes per workday). Participants also wore an ActiGraph accelerometer for the seven days in between the test and retest, recording the times they wore the accelerometer, the days they worked, and their work times in a logbook. Analyses determined test-retest reliability with intraclass correlation coefficients (ICC) and assessed criterion validity against accelerometers using Spearman’s rho.

Results The test-retest ICCs for occupational sitting, standing and walking for ranged 0.73-0.90 for OSPAQ-min and ranged 0.75-0.95 for OSPAQ-percent. Spearman’s correlation coefficients between accelerometer-measured sedentary time at work and self-reported sitting time at work suggested moderate to high correlations (OMS-min, r=0.65; OMS-percent, r=0.50). Moderate validity correlations were found for measuring standing at work (OMS-min, r=0.49; OMS-percent, r=0.54). Validity correlations for measuring walking at work were lower (OMS-min, r=0.29; OMS-percent, r=0.26).

Discussion and Conclusion The OSPAQ has excellent test-retest reliability and moderate to high validity for estimating relative and absolute time spent sitting and standing at work and is comparable to existing occupational physical activity measures for assessing time spent walking at work. Future research would help refine the OSPAQ by investigating the generalize ability of the instrument to other population subgroups, such as men, people with lower levels of education, and workers in less sedentary or more physically active or demanding occupations.

The OSPAQ brief instrument measures sitting and standing at work as distinct behaviors and would be suitable for use in large samples and in studies measuring numerous health behaviours and outcomes.

References [1] van Uffelen, J.G.Z., Wong, J., Chau, J.Y., van der Ploeg, H.P., Riphagen, I., Gilson, N., Burton, N.W., et al. Occupational sitting and health risks: A systematic review. Am J Prev Med, 2010; 39, 379-388. [2] Kwak, L., Proper, K.I., Hagströmer, M., Sjöström, M. The repeatability and validity of questionnaires assessing occupational physical activity – a systematic review. Scand J Work Environ Health; 2010 Aug 30. [Epub ahead of print]