Change in physical activity and its association with decline in kidney function: A UK Biobank-based cohort study.

Previous research on the association between physical activity (PA) and kidney function is inconsistent. The association between muscle mass and serum creatinine (SCr) may have implications for interpreting the effect of PA on estimated glomerular filtration rate (eGFR).

Few studies have reported changes in physical activity and changes in kidney function. A cohort study was constructed using the UK Biobank.

Changes in physical activity were self-reported as metabolic equivalent task (MET) minutes/week. eGFR was calculated using SCr and cystatin C (CysC).

Cox and nonlinear regressions with restricted cubic splines were applied to explore the association between changes in physical activity and rapid decline of kidney function (RDKF, eGFR annual decrease ≥3 mL/min/1.73 m), and the annual change of eGFR. An exploratory analysis of cardiorespiratory fitness as the exposure was conducted.

Among 11 757 participants, the median follow-up time was 4.4 years. Participants whose PA decreased by 1000 MET minutes/week at the follow-up assessment had a 2% reduction in risk of developing RDKF (HR = 0.98, 95% CI: 0.96, 1.00).

In contrast, a 1000 MET minutes/week increase in PA was associated with a 4% reduction in risk of developing RDKF (HR = 0.96, 95% CI: 0.93, 0.99). A PA increase of 1000 MET minutes/week was associated with eGFR annual increase of 0.04 mL/min/1.73 m (95% CI: 0.03, 0.06) but no significant changes in eGFR.

In this general population study, there are differing associations between changes in PA and changes in kidney function depending on the kidney biomarker used. Increasing PA is modestly associated with improving annual eGFR and reduced risk of RDKF.