Relationship between objectively measured sedentary behaviour and functional capacity in older adults

INTRODUCTION Sedentary behaviour is an independent risk factors for all major chronic diseases, disablement and frailty1. Older adults are the most sedentary segment of the population2. Little is know about the relationship between sedentary behaviour and functional capacity in older adults. METHODS This cross-sectional study received ethical approval from Northumbria University School of Psychology and Sports Science Ethics Committee. Fifty-six community dwelling older adults with an average age 79 (SD=4) years including 26 male and 30 females were recruited. The participants functional capacity was assessed using their gait speed, measured over a 10 meter walk and a GAITRite system, and the Timed Up and Go (TUG) test. Participants wore an ActivPAL activity monitor continuously for 7 days which registered the time and length of sitting periods which are used to identify bouts of sedentary time. The daily mean sedentary time and variability in individual bouts of sedentary time (standard deviation of individuals daily mean) was computed for each participant. The relationship between sedentary behaviour and functional capacity (represented by gait speed and TUG) was investigated using generalised linear model corrected for gender and age with the sedentary variables as response variables and functional capacity variables as predictors (linear combination of walking speed and TUG). RESULTS Mean daily sedentary time was 690 (min) and variability of sedentary time (within subject standard deviation) was 115 (min). Day to day variability varied from 20 to 250 (min) with a mean of 79 (min) for the sample. The generalised linear model showed significant association between higher functional capacity and lower total time spent sedentary and functional variables p=0.035) with gait speed and TUG explaining 13% of the variance. Both higher gait speed and lower TUG were also significant predictors of higher day to day variability in sedentary time (p = 0.01) accounting for 24 DISCUSSION AND CONCLUSION Higher functional capacity appears associated with less sedentary time and a more variable pattern of sedentary behaviour. Functional capacity appears to have a stronger effect on variability of sedentary time than on total sedentary time suggesting. This suggests that increased functional capacity might not directly lead to decrease in sedentary time but might empower older adults to modulate the time they spend sedentary. It is also possible that a higher variability in sedentary behaviour and hence a more flexible pattern could be a predictor of response to interventions aimed at reducing sedentarity.