Effects of Isotemporal Substitution Analysis of Sedentary Behavior, Sleep, and Physical Activity on Physical Performance in Older Adults

Analyze the effects of substituting time spent in sleep, sedentary behavior, and moderate-to-vigorous physical activity on the physical performance of older adults. The sample consisted of 457 participants from the Alcobaça Elderly Health Longitudinal Study. Physical performance was measured using the Short Physical Performance Battery, while physical activity and sedentary behavior were assessed with the International Physical Activity Questionnaire, and sleep with the Pittsburgh Sleep Quality Index. For statistical analysis, the isotemporal substitution approach was applied to examine the hypothetical effects of reallocating time between sleep, sedentary behavior, and moderate-to-vigorous physical activity on physical performance. The results showed that substituting small periods of sleep or sedentary behavior with moderate-to-vigorous physical activity was associated with a significant reduction in the risk of poor physical performance. The reallocation of just 5 min/day already showed a protective effect (a reduction of 13% to 14%), with an increasing impact proportional to the amount of time replaced, reaching an 82% reduction for 60 min/day. Model-based analyses suggest that replacing short periods of sedentary behavior or sleep with moderate-to-vigorous physical activity is associated with a lower risk of poor physical performance in older adults.