Assessment of physical activity in older individuals: a doubly labeled water study

We compared the accuracy of two physical activity recall questionnaires and a motion detector in 45- to 84-yr-old women ( n = 35) and men ( n = 32), using doubly labeled water (DLW) in conjunction with indirect calorimetry as the criterion measure. Subjects were administered the Yale Physical Activity Survey (YPAS) and Minnesota Leisure Time Physical Activity Questionnaire (LTA). Physical activity energy expenditure was determined over a 10-day period by using a Caltrac uniaxial accelerometer and DLW in conjunction with indirect calorimetry. In older women, Minnesota LTA (386 ± 228 kcal/day) and Caltrac (379 ± 162 kcal/day) underestimated physical activity by ∼55% compared with DLW (873 ± 244 kcal/day). No difference was observed between daily physical activity measured by the YPAS (863 ± 447 kcal/day) and DLW in older women. In older men, Minnesota LTA (459 ± 288 kcal/day) and Caltrac (554 ± 242 kcal/day) underestimated daily physical activity by ∼50–60% compared with DLW (1,211 ± 429 kcal/day). No difference was found between physical activity measured by the YPAS (1,107 ± 612 kcal/day) and DLW in older men. Despite no difference in mean physical activity levels between YPAS and DLW in women and men, Bland and Altman ( Lancet 1: 307–310, 1986) analyses demonstrated poor concordance between DLW and YPAS (i.e., limits of agreement = −1,310–1,518 kcal/day). Our data suggest that the Minnesota LTA recall and Caltrac uniaxial accelerometer may significantly underestimate free-living daily physical activity energy expenditure in older women and men. Although the YPAS compares favorably with DLW on a group basis, its use as a proxy measure of individual daily physical activity energy expenditure may be limited in older women and men.