Prolonged sitting time and all-cause mortality: the mediating and predictive role of kidney function markers.

Objective: To investigate the association between daily sitting time and all-cause mortality, with a focus on the mediating effect and predictive value of the makers relating to kidney.

Methods: The cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) from 2003 to 2020. The makers relating to kidney were assessed through estimated glomerular filtration rate (eGFR), urine albumin creatinine ratio (UACR), and other relevant markers.

Results: A total of 9,707 adults were included in the analysis. There was a significant increase in the levels of blood urea nitrogen (BUN), creatinine, uric acid, osmolality, and UACR with extended daily sitting time, while eGFR significantly decreased. Notably, individuals sitting ≥ 8 h per day exhibited a 67% higher risk of all-cause mortality (HR = 1.67, 95% CI: 1.43-1.94). A nonlinear (L-shaped) relationship was observed between eGFR (p < 0.001) or UACR (p < 0.001) and all-cause mortality. Mediation analysis revealed that eGFR accounted for 20.98% of the association between sitting time and mortality (p < 0.01). An addition of eGFR or UACR would increase the AUC from 0.585 to 0.762 and 0.656, respectively(p < 0.001). The main mortality caused by daily sitting time included chronic lower respiratory diseases, diabetes mellitus, cerebrovascular diseases and heart diseases.

Conclusions: Prolonged daily sitting time is significantly associated with an increased risk of all-cause mortality, potentially mediated by impaired kidney function. Incorporating kidney function markers such as eGFR and UACR enhances the predictive value for mortality risk assessment in sedentary populations.