Sedentary behaviour, physical activity, and renal function in older adults: isotemporal substitution modelling

BackgroundPhysical inactivity and sedentary behaviour (too much sitting) can contribute to renal dysfunction. However, the potential benefits of behavioural change (e.g. replacing sedentary behaviour with physical activity) on renal function are not well understood. We used isotemporal substitution to model potential impacts of behaviours on renal function by replacing time spent in one behaviour to another.MethodsIn 174 older Japanese adults (age, 50-83years; females, 76%), the time spent in sedentary behaviour, light-intensity physical activity (LPA), and moderate- to vigorous-intensity physical activity (MVPA) were assessed using an uniaxial accelerometer. Renal function was evaluated by the estimated glomerular filtration rate (eGFR) from serum creatinine and cystatin C levels.ResultsIn univariate analyses, eGFR was significantly, albeit weakly, correlated with time spent in sedentary behaviour (r(s)=-0.229), LPA (r(s)=0.265), and MVPA (r(s)=0.353). In the isotemporal substitution models, replacement of 30min/day of sedentary behaviour with an equivalent LPA time was not significantly associated with eGFR (beta =2.26, p=0.112); however, replacement with an equivalent time of MVPA was beneficially associated with eGFR (beta =5.49, p