Isotemporal Substitution of Sedentary Behavior and Physical Activity on Functional Performance in Older Adults: 1908 Board #1 June 1 3

Age-related progressive increases in sedentary behavior (SB) and decreases in physical activity (PA) have been independently linked to deficits in functional capacity in older adults. The independent relationship of PA and SB on functionality and the lack of evidence for PA interventions to alter SB have led to an interest in joint interventions to displace SB with a PA. PURPOSE: To examine the relationship of substituting 30 minutes of SB with light (LPA) and moderate-to-vigorous physical activity (MVPA) on functional performance in community dwelling older adults. METHODS: A hip-worn accelerometer (ACC, Actigraph GT3X+) was worn for seven consecutive days to collect human movement. Freedson cut-points and Choi algorithm for wear-time were used to determine SB, LPA, and MVPA. Functional measures included 400m walk test (400W; m/sec), usual gait speed (UGS; m/sec), and 5-time sit-to-stand (STS; sec). Isotemporal substitution modeling was used to predict the relationship of substituting 30 minutes spent in SB, LPA, and MVPA while adjusting for age and gender. RESULTS: Ninety-one older adults (60% female) aged 50-90 years with an average ACC wear time of 13.99 ± 0.13 hr/day spent approximately 63% of waking hours in SB. LPA was a significant predictor of 400W [β= 0.032 m/sec (95% CI: 0.006, 0.056)] and MVPA for 400W [0.204 m/sec (0.110, 0.297)], UGS [-0.618 sec (-0.178, -0.1.059)], and STS [-2.276 sec (-3.714,-0.759)]. Directly substituting 30 minutes of SB time with LPA resulted in a significant improvement in 400W [0.027 m/sec (0.000, 0.053)]. MVPA significantly improved 400W [0.193 m/sec (0.099, 0.286)], UGS [0.575 sec (0.123, 1.020)], and STS [-2.176 sec (-3.734,-0.753)]. Aside from a strict 1:1 reallocation of SB to LPA or MVPA, significant improvements in all functional measures were observed with a combination of 5 minutes MVPA and 25 minutes LPA. CONCLUSIONS: While MVPA had the greatest impact when displacing SB, the practical implications of introducing a LPA to displace SB may be of particular importance among public health practitioners. Specifically, a goal of redirecting 5-10% of SB time (27–54 minutes/day) toward LPA, and not exclusively MPVA, may result in beneficial changes in functional health in older adults.