Associations Between the Vitamin D Levels and Urine Albumin-to-Creatinine Ratio in Adults With Hypertension

Rationale & Objective Hypertension is a major risk factor for cardiovascular and kidney diseases. While an elevated urinary albumin-to-creatinine ratio (UACR) — even within the normal range — predicts increased cardiovascular risk, and vitamin D is associated with UACR in general populations, this relationship remains unclear in individuals with hypertension. Study Design This study employed a cross-sectional design using data from the National Health and Nutrition Examination Survey (NHANES, 1999–2018). Setting & Participants The study involved a cohort of 37,554 individuals, comprising 19,802 hypertensive patients and 17,752 non-hypertensive individuals from the United States, with a mean age of 46.7 ± 16.8 years. Exposure Serum vitamin D levels. Outcome UACR. Analytical Approach Survey-weighted multivariable regression models were applied to assess the relationship between vitamin D and log 2 -transformed UACR. Restricted cubic splines, subgroup analyses, and sensitivity analyses were conducted to examine the nature and robustness of the association. Results In hypertensive patients, the inverse association between vitamin D and UACR was more pronounced than in non-hypertensive individuals (P for interaction=0.03). Vitamin D deficiency was associated with 17.3% higher geometric mean UACR (β = 0.23) compared to insufficiency, whereas sufficient levels showed no significant difference (P = 0.51). A threshold effect was identified at approximately 60 nmol/l, with levels below this point showing a significant negative correlation (β = -0.14, equivalent to a 9.3% reduction in UACR, P<0.001). These consistent findings were corroborated by subgroup and sensitivity analyses. Limitations The observational design precludes causal inferences, and residual confounding may persist despite adjustments. Generalizability may be limited, as data were derived from a single U.S. cohort, and both vitamin D and UACR relied on single measurements. Conclusions There is an L-shaped inverse association between serum vitamin D levels and UACR among U.S. adults with hypertension.