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), usi ng doubly labeled water (DLW) in conjunction with indirect calorimetry as t he 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 per iod by using a Caltrac uniaxial accelerometer and DLW in conjunction with i ndirect calorimetry. In older women, Minnesota LTA (386 +/- 228 kcal/day) a nd Caltrac (379 +/- 162 kcal/day) underestimated physical activity by simil ar to 55% compared with DLW (873 +/- 244 kcal/day). No difference was obser ved 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 activ ity by similar to 50-60% compared with DLW (1,211 +/- 429 kcal/day). No dif ference 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 (L ancet 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 sugg est that the Minnesota LTA recall and Caltrac uniaxial accelerometer may si gnificantly underestimate free-living daily physical activity energy expend iture 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.