Low daily physical activity has been linked to poor health and functional performance with aging. However, the health implications of the daily patterns/temporal accumulation of physical activity remain unknown. We created an activity fragmentation index (AFI) to account for the number and duration of daily active bouts using 7-day accelerometry data from the Baltimore Longitudinal Study of Aging (n = 734, mean age 67.8 ± 13.2 years, 50% female). Minute-epoch activity counts were dichotomized into active or sedentary states, and summarized according to the distribution of active bout durations. AFI was calculated as the reciprocal of the average duration of the active bouts. Total daily volume of physical activity was summarized using total log-transformed activity counts (TLAC). Using multiple linear regression models adjusted for age, sex, height, weight, TLAC, and disease conditions, AFI was negatively associated with gait speed (β = -0.06 m/s, p < 0.004), and positively associated with laboratory assessments of high fatigability (p < 0.001). TLAC was a significant predictor of gait speed and fatigability until AFI was added to the model, suggesting that the duration and number of active bouts throughout the day mediates the associations among TLAC, gait speed, and fatigability. Together, these results imply that accounting for fragmented daily physical activity may be more important than total volume of physical activity when assessing functional performance in older adults. Further research is needed to validate this measure and determine the longitudinal value of activity fragmentation in predicting adverse outcomes in older adults.
展开▼
