Association between plasma eosinophil count and chronic kidney disease: results from the NHANES 2005-2018 and Mendelian randomization study

Background : This investigation seeks to examine the association between plasma eosinophil count(PEC) and the risk of chronic kidney disease (CKD) and related traits such as estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR), additionally elucidating the causal relationship via Mendelian Randomization (MR) analysis. Methods : To evaluate the association between PEC and the risk of CKD and related traits, weighted multivariable-adjusted logistic regression was conducted using data from the NHANES 2005–2018. Survival curve analysis was also employed to examine the relationship between PEC and prognosis in CKD patients. Furthermore, a two-sample MR study leveraged genome-wide association study (GWAS) summary statistics to explore the causal links between PEC and CKD, eGFR, and UACR. The primary inverse variance weighted (IVW) method, alongside supplementary MR techniques, was used to verify these causal associations. Pleiotropy and heterogeneity analyses were performed to ensure the robustness of the results. Results : A total of 36,291 participants were included in the NHANES observational study. Weighted multivariable-adjusted logistic regression indicated that PEC was significantly associated with a higher risk of CKD (odds ratio [OR] = 1.654; 95% confidence interval [CI], 1.413–1.936). PEC also showed a strong positive correlation with both lower eGFR and elevated UACR (≥ 30 mg/g). Kaplan-Meier survival analysis revealed that higher eosinophil counts were linked to worse long-term survival in CKD patients. MR analyses further supported a causal link between genetically predicted PEC and increased CKD risk (odds ratio [OR], 1.095 [95% CI, 1.026–1.169]; P  = 0.006). A causal relationship between PEC and eGFR (OR, 0.991 [95% CI, 0.985–0.996]; P  = 0.001) was also observed. However, no significant association was identified between PEC and UACR (OR, 1.044 [95% CI, 0.906–1.204]; P  = 0.547). Pleiotropy and heterogeneity analyses were conducted to confirm the robustness of the findings. Conclusion : PEC shows a significant association with CKD and reduced eGFR, suggesting a potential causal role in their development. While PEC is also significantly linked to UACR, the MR analysis found no evidence of a causal relationship between PEC and UACR.