Dose-response association between physical activity and sedentary time categories on ageing biomarkers

Background Physical activity and sedentary behaviour have been suggested to independently affect a number of health outcomes. To what extent different combinations of physical activity and sedentary behaviour may influence physical function and frailty outcomes in older adults is unknown. The aim of this study was to examine the combination of mutually exclusive categories of accelerometer-measured physical activity and sedentary time on physical function and frailty in older adults. Methods 771 older adults (54% women; 76.8 +/- 4.9 years) from the Toledo Study for Healthy Aging participated in this cross-sectional study. Physical activity and sedentary time were measured by accelerometry. Physically active was defined as meeting current aerobic guidelines for older adults proposed by the World Health Organization. Low sedentary was defined as residing in the lowest quartile of the light physical activity-to-sedentary time ratio. Participants were then classified into one of four mutually exclusive movement patterns: (1) 'physically active & low sedentary', (2) 'physically active & high sedentary', (3) 'physically inactive & low sedentary', and (4) 'physically inactive & high sedentary'. The Short Physical Performance Battery was used to measure physical function and frailty was assessed using the Frailty Trait Scale. Results 'Physically active & low sedentary' and 'physically active & high sedentary' individuals had significantly higher levels of physical function (beta = 1.73 and beta = 1.30 respectively; all p < 0.001) and lower frailty (beta = - 13.96 and beta = - 8.71 respectively; all p < 0.001) compared to 'physically inactive & high sedentary' participants. Likewise, 'physically inactive & low sedentary' group had significantly lower frailty (beta = - 2.50; p = 0.05), but significance was not reached for physical function. Conclusions We found a dose-response association of the different movement patterns analysed in this study with physical function and frailty. Meeting the physical activity guidelines was associated with the most beneficial physical function and frailty profiles in our sample. Among inactive people, more light intensity relative to sedentary time was associated with better frailty status. These results point out to the possibility of stepwise interventions (i.e. targeting less strenuous activities) to promote successful aging, particularly in inactive older adults.