Association between vitamin D deficiency and chronic kidney disease progression: A GRADE-based dose-response...

This systematic review and dose-response meta-analysis aimed to evaluate the association between serum vitamin D status and chronic kidney disease (CKD) progression.

We searched PubMed, Scopus, Web of Science, and Embase for relevant observational and cohort studies published between 1990 and 2024. Eligible studies reported baseline vitamin D levels and CKD progression outcomes. We performed a random-effects meta-analysis to calculate the pooled odds ratio (OR) for CKD progression. A dose-response meta-analysis examined the relationship between serum 25-hydroxyvitamin D (25(OH)D) levels and risk, while subgroup analyses explored follow-up duration, study quality, and comorbid conditions. We assessed evidence certainty using the Grading of Recommendations Assessment, Development and Evaluation approach.

Eleven studies met the inclusion criteria. The pooled analysis suggested that vitamin D deficiency was associated with 33% higher odds of CKD progression (OR = 1.33, 95% confidence interval [CI]: 1.06-1.67; P = .019); however, between-study heterogeneity was considerable (I-squared heterogeneity statistic [I2] = 98.2%). The pooled estimate should therefore be interpreted cautiously as an average association across heterogeneous studies. A dose-response analysis of 10 studies suggested higher odds of CKD progression per 10 ng/mL lower 25(OH)D concentration (OR = 1.18, 95% CI: 1.09-1.25), although its interpretation was limited by reconstructed category-level exposure values. Subgroup analyses showed stronger associations in studies with long-term follow-up (≥5 years; OR = 2.07, 95% CI: 1.29-3.14; P = .001) and high-quality studies (OR = 1.35, 95% CI: 1.06-1.69; P = .03). The Grading of Recommendations Assessment, Development and Evaluation assessment rated the certainty of evidence as very low for the overall association and low for the dose-response analysis, primarily because of the observational study designs and substantial between-study heterogeneity.

Lower serum 25(OH)D levels were associated with higher odds of CKD progression. However, the observational nature of the evidence does not establish that routine screening or vitamin D supplementation can prevent renal function decline. Prospective studies and randomized trials are needed to clarify the clinical utility of vitamin D assessment and supplementation for renal outcomes.