The neutrophil percentage to albumin ratio as a predictor of all-cause and cardiovascular mortality in patients with diabetic kidney disease: A longitudinal cohort analysis of NHANES 2009 to 2018

The relationship between neutrophil percentage to albumin (NPAR) index and mortality in patients with diabetic kidney disease (DKD) remains unclear. This study aimed to investigate this association by designing a nationally representative longitudinal cohort. We conducted a longitudinal cohort analysis of 1778 adults with DKD from the National Health and Nutrition Examination Survey (2009-2018) with linkage to mortality data through December 31, 2019. Multivariate Cox proportional hazards models were conducted to explore the correlation between the NPAR index and all-cause and cardiovascular disease (CVD) mortality. A restricted cubic spline analysis was performed to explore the potential nonlinear relationship. Additionally, subgroup and sensitivity analysis were conducted to ensure the robustness of the findings. Over a median follow-up of 71 months (84,604 person-years), 462 all-cause and 146 CVD deaths occurred. Compared to the lowest quartile, participants in the highest NPAR quartile had significantly increased risks of all-cause (hazard ratio 1.96, 95% confidence interval 1.49-2.58, P < .001) and CVD mortality (hazard ratio 3.62, 95% confidence interval 2.04-6.41, P < .001). Restricted cubic spline analysis revealed a J-shaped relationship between NPAR and all-cause mortality (P for nonlinearity < .001), whereas NPAR showed a linear positive association with CVD mortality (P for nonlinearity = .4771). These findings remained consistent across subgroup and sensitivity analysis. Higher NPAR is independently associated with increased risks of all-cause and cardiovascular mortality in adults with DKD, supporting its potential role as a prognostic biomarker.