The 25(OH)D deficiency is a prevalent issue among patients with chronic kidney disease (CKD). The aim of our study is to investigate whether low levels of 25(OH)D are associated with increased all-cause and cardiovascular mortality in patients with CKD.

This retrospective cohort study utilized the National Health and Nutrition Examination Survey (NHANES) and the National Death Index (NDI) 2007—2018 database to investigate the association between 25(OH)D levels and all-cause mortality as well as cardiovascular mortality. A total of 2 668 eligible subjects were included in this study, with follow-up conducted until December 31, 2019. Cox proportional hazards regression, restricted cubic spline, Kaplan-Meier survival curves, and competing risk survival analysis were performed to evaluate the associations. Furthermore, subgroup and sensitivity analyses were performed.

During a median follow-up of 6 years in a weighted population of 11 715 452 eligible participants, there were 665 deaths from any cause, including 196 cardiovascular-related deaths. After adjusting for covariates, lower levels of 25(OH)D were significantly associated with increased risks for both all-cause (HR=0.85, 95%CI: 0.77-0.94) and cardiovascular mortality (SHR=0.80, 95%CI: 0.67-0.94). Consistent results were also observed when analyzing 25(OH)D as a categorical variable (quartile) (both P<0.05). Weighted restricted cubic splines revealed an inverse J-shaped association between levels of 25 (OH) D and all-cause mortality (P_nonliner> 0.05). Subgroup analysis (P_interaction>0.05) and sensitivity analysis (HR=0.85, 95%CI: 0.77-0.93) yielded similar findings.

Lower 25(OH)D levels, both as a continuous and categorical variable, are significantly associated with an increased risk of all-cause mortality and cardiovascular disease-related mortality.The 25(OH)D has a negative j-shaped association with all-cause and cardiovascular mortality.