Association between urinary nickel levels and impaired kidney function in older adults aged 65 years and above in 18 longevity areas in China

Objective: To explore the association between urinary nickel levels and impaired renal function in older adults aged ≥65 years from 18 longevity regions of China. Methods: Based on the 2021 China Healthy Ageing and Biomarkers Cohort Study, 5 045 participants were enrolled. Venous blood and urine samples were collected to detect renal function-related indicators and urinary nickel. Impaired renal function was jointly determined by calculating the estimated glomerular filtration rate and urinary albumin-creatinine ratio, and urinary nickel levels were adjusted by urinary creatinine. To assess the relationship between urinary nickel levels and impaired kidney function, we used multivariate logistic regression. Restricted cubic splines were applied to examine the dose-response relationship, with additional subgroup analyses and interaction analyses performed. Results: The median age of participants was 83.40 years, 54.73% of whom were female, and the median urinary nickel level was 2.10 μg/L. Following adjustment for covariates in the multivariate logistic regression analysis, the comparison with the Q₁ revealed that the Q₄ group of urinary nickel had a 26% increased risk of impaired renal function (OR=1.26, 95%CI: 1.05-1.51). Dose-response analysis revealed a positive nonlinear association between urinary creatinine-adjusted urinary nickel and impaired renal function (all P for overall <0.05, nonlinear P<0.05). Subgroup and interaction analyses indicated that the association between urinary nickel and impaired renal function was more significant in men, Han Chinese, and non-diabetic populations, with significant interaction effects (all P<0.05). Conclusion: The risk of impaired renal function increases with elevated urinary nickel levels in older adults aged ≥65 years from 18 longevity areas of China.