Age modify the associations of obesity, physical activity, vision and grip strength with functional mobility in Irish...

To estimate whether the associations of obesity, physical activity, vision and grip strength with functional mobility were modified by age.

Data from The Irish Longitudinal Study on Ageing (2009-2012) were analyzed and 5001 individuals were included in this study. Mobility was assessed by the timed up and go test (TUG-test). Main exposure variables were obesity, physical activity, visual acuity and grip strength at baseline. Multiple linear regression models were fitted to assess the associations of baseline main exposure variables with 2-year follow-up functional mobility and potential confounders were adjusted. Stratified analyses by age were used to assess the interaction between main exposures and age on functional mobility.

Multiple linear regression models identified significant interactions of obesity (P < 0.001), vigorous physical activity (P = 0.001), vision (P < 0.001) and grip strength (P < 0.001) with age on functional mobility. Stratified analyses suggested that the risk effect of obesity on functional mobility was greater in middle-aged group (β = 0.025, P < 0.001) than in older group (β = 0.016, P = 0.017). The protective effects of high level of physical activity and grip strength on functional mobility were stronger in older group (β = -0.023, P = 0.004 for physical activity; β = -0.002, P < 0.001 for grip strength) than in middle-aged group (β = -0.012, P = 0.008 for physical activity; β = -0.0015, P < 0.001 for grip strength). The benefit of better vision on functional mobility was observed in middle-aged group only (β = -0.032, P = 0.002).

Non-obesity, higher level of physical activity, vision and grip strength at baseline were associated with better mobility performance among middle-aged and older Irish. And these associations were modified by age.