Abstract
INTRODUCTION: Despite the existence of numerous studies highlighting the adverse effects of smoking on kidney function, the investigation of the correlation between serum cotinine and chronic kidney disease (CKD) remains inconclusive due to insufficient evidence. Consequently, the primary objective of this study was to ascertain the association between serum cotinine levels and CKD. METHODS: This study analyzed data from 10900 Americans participating in the National Health and Nutrition Examination Survey between 2005 and 2016. The independent variable under investigation was log serum cotinine, while the dependent variable was the presence of CKD. To investigate the potential linear and non-linear correlations between serum cotinine and CKD, logistic regression models and generalized additive models (GAM) were employed. Furthermore, stratified analyses and interaction tests were conducted to evaluate potential disparities in the relationship between serum cotinine and CKD, based on sex. RESULTS: The median age in the study participants was 49.28 ± 17.96 years, and the median log serum cotinine (ng/mL) was -0.54 ± 1.68. The prevalence of CKD was found to be 17.04%. Multifactorial regression analysis did not show a statistically significant association between log serum cotinine and CKD (OR=1.02; 95% CI: 0.98-1.06, p=0.4387). A statistically significant non-linear association between log serum cotinine and CKD was also not observed in the GAM analysis (p non-linear value=0.091). Subgroup analyses revealed sex differences in the association between log serum cotinine and CKD. Briefly, males had a positive association between log serum cotinine and incident CKD (OR=1.08; 95% CI: 1.02-1.15, p=0.0049). In females, there was a U-shaped association between log serum cotinine and CKD, with an optimal inflection point for log serum cotinine of -0.30 (serum cotinine=0.5 ng/mL). CONCLUSIONS: Cross-sectional analyses of NHANES data showed gender differences in the association between serum cotinine and the development of CKD.