Serum 25-Hydroxyvitamin D were associated with higher risk of both albuminuria and impaired GFR incidence: a cohort study based on CLHLS study.

BACKGROUND: This study aimed to examine the relationship between 25-hyfromxyvitamin D (25OHD) and chronic kidney disease (CKD) incidence.

METHODS: All the elderly who had participated both in the 2011-2012 survey and 2014 survey in the Chinese Longitudinal Healthy Longevity Survey (CLHLS), and have biomarker data were included in the analysis. We studied those without CKD with complete data at 2011-2012 waves. Serum 25-Hydroxyvitamin D was assessed at baseline. Cox proportional risk model was used to evaluate associations between serum 25-Hydroxyvitamin D and CKD (including both albuminuria and impaired eGFR) incidence after adjusted for potential confounding..

RESULTS: During the follow-up years, 255 incident cases of CKD were diagnosed. Those who developed CKD had relatively lower serum 25(OH)D (mean 37.63 vs.51.36 nmol/L, p < 0.001) compared with those who remained free of CKD. Each 1 nmol/L increase in 25(OH)D was associated with 3.4% reduced risk of CKD (HR = 0.966, 95%CI: 0.959-0.973) after adjusted for related covariates. The HRs of each 1 nmol/L increase in 25(OH)D for albuminuria and impaired eGFR were 0.952(95%CI: 0.941-0.963) and 0.975(95%CI: 0.966-0.983) respectively. When use the classifications (sufficiency, insufficiency, deficiency) or quintiles of baseline 25(OH)D levels in the Cox model, the corresponding HRs showed an increasing trend along with the decrease of baseline 25(OH)D levels (p for trend < 0.001).

CONCLUSIONS: Higher 25(OH)D levels were inversely and independently associated with CKD incidence among Chinese elderly. The trend for the observed linear relationship b was most pronounced among the lowest quintile.