Objective. To evaluate the correlation between the Yale Physical Activity Survey (YPAS) scores and objective accelerometer measures of time spent in light intensity physical activities, moderate to vigorous intensity physical activities, and moderate to vigorous activities in bouts lasting at least 10 minutes. Methods. This study analyzed baseline data from 171 persons with rheumatoid arthritis (RA) and 139 persons with osteoarthritis (OA) in a randomized clinical trial (Increasing Motivation for Physical Activity in Arthritis Clinical Trial). Persons fulfilling the 1987 American College of Rheumatology criteria for RA and persons with symptomatic radiologic knee OA (Kellgren/Lawrence class >2) wore an accelerometer for 7 days, then responded to the YPAS questionnaire and questions regarding demographics (age, sex, and race) and health factors (body mass index, disease status [Health Assessment Questionnaire/Western Ontario and McMaster Universities Osteoarthritis Index], comorbidities, pain, and function). Spearman's correlation coefficients were estimated between each YPAS summary measure and accelerometer measures. Results. In the RA participants, the strongest correlation was between the YPAS activity dimensions summary index (Y-ADSI) and average daily minutes of bouted moderate/vigorous activity (r = 0.51). Additionally, the Y-ADSI correlated significantly with both objectively measured average daily accelerometer counts (r = 0.45) and average daily minutes of moderate/vigorous activity (r = 0.43). For OA participants, a similar pattern emerged: the Y-ADSI had significant correlations with average daily minutes of bouted moderate/vigorous activity (r = 0.36), average daily minutes of moderate/vigorous activity (r = 0.31), and average daily counts (r = 0.24). Conclusion. For both the RA and OA groups, the Y-ADSI had the strongest significant correlations with objectively measured physical activity, which supports Y-ADSI use as a tool for clinical applications and in rheumatology research.
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