The Association between the Platelet to White Blood Cell Ratio and Chronic Kidney Disease in an Aging Population: A Four-Year Follow-Up Study

Introduction: The platelet to white blood cell ratio (PWR) has been reported to be a prognostic factor for some diseases, such as subarachnoid hemorrhage. However, the association between the PWR and chronic kidney disease (CKD) remains unknown. To investigate the cross-sectional and longitudinal association between the PWR and CKD, this study was performed. Methods: This study used datasets from a national prospective cohort in China (China Health and Retirement Longitudinal Study). A retrospective cohort from 2011 to 2015 was constructed. The PWR was stratified as a categorical variable according to tertiles (T1–T3 groups). CKD was defined as an estimated glomerular filtration rate < 60 mL min(−1)/1.73/m(2). Univariate and multivariate logistic regressions and restricted cubic spline regression were adopted to assess the linear and non-linear association between the PWR and CKD. Propensity score matching was used to balance the discrepancies between covariates. Subgroup and interactive analyses were performed to explore potential interactive effects of covariates. Missing values were interpolated using random forest. The PWR was also stratified according to the median and quartiles as sensitivity analyses. Results: A total of 8600 participants were included in this study. In the full model, the odds ratios (ORs) of prevalent CKD were 0.78 (95% CI = 0.62–0.97, p < 0.05) for the T2 group and 0.59 (95% CI = 0.46–0.76, p < 0.001) for the T3 group. There were significant interactive effects of marital status and smoking in the PWR–CKD association (both p for interaction < 0.05). An L-shaped, non-linear association was detected between the PWR and prevalent CKD in the overall population, participants ≥ 60 years, and females subgroups (all p for non-linear < 0.05). All sensitivity analyses supported the negative association between the PWR and prevalent CKD. In the 2011–2015 follow-up cohort, the ORs of incident CKD were 0.73 (95% CI = 0.49–1.08, p > 0.05) and 0.31 (95% CI = 0.18–0.51, p < 0.001) for the T2 and T3 groups, respectively, in the full model. Conclusions: A high PWR is associated with a reduced risk of prevalent and incident CKD. The PWR may serve as a predictor for CKD, facilitating the early identification and intervention of kidney function decline.