Association of Serum Vitamin D Levels with Cardiovascular and All-Cause Mortality among Kidney Stone Formers: The National Health and Nutrition Examination Survey, 1988-1994 and 2007-2018

Background: The associations between serum 25-hydroxy-vitamin D (25D) levels and mortality outcomes in individuals with kidney stone disease (KSD) remain unclear. Methods: We assessed the relationship between 25D levels and mortality among a sample of US adults (age ≥20 years), using the National Health and Nutrition Examination Survey (NHANES) 1988-1994 and 2011-2018, and its Linked Mortality File (through 2019). KSD was defined as a self-report of any previous episode of kidney stone. Cox proportional hazard regression analyses were used to estimate the risks of all-cause and cardiovascular disease (CVD) mortality. Results: We included 42,207 participants in the analysis; among them, 3,378 had KSD. Stone formers (SF) tended to be male, white, and older, had a higher BMI, and were more likely to have hypertension, diabetes, and CVD. However, the estimated GFR was similar between SF and non-SF. Among SF, the mean serum 25D was 69.1 ng/ml, there were 749 all-cause deaths and 209 CVD deaths with a median follow-up of 7.8 years, whereas among non-SF, the mean serum 25D was 66.6 ng/ml, and there were 7,761 all-cause deaths and 2,231 CVD deaths with a median follow up of 10.3 years. In both unadjusted and adjusted analyses, unlike non-SF where higher serum 25D was associated with a lower risk for death and CVD death, higher serum 25D was associated with a lower risk for CVD death but not all-cause death in SF [Table]. Conclusion: Among SF, higher serum 25D was associated with a reduced risk for CVD death but not all-cause death. Future prospective studies are needed to clarify the effect of 25D on survival among SF. Funding: Private Foundation Support Hazard ratios for 25D* and mortality by KSD - Stone Formers Non-Stone Formers CVD Mortality All-cause Mortality CVD Mortality All-cause Mortality Model HR 95% CI HR 95% CI HR 95% CI HR 95% CI Unadjusted 0.92 0.84-0.99 0.98 0.93-1.03 0.92 0.88-0.95 0.93 0.91-0.95 Adjusted 0.89 0.82-0.97 0.97 0.92-1.01 0.94 0.91-0.97 0.95 0.93-0.97 *Per 10 nmol/L. **Age, sex, race/ethnicity, education, health insurance, BMI, hypertension, diabetes, CVD, smoking, alcohol intake, thiazide use, leisure physical activity intensity; dietary intake of total fluid, sodium, potassium, magnesium; serum total cholesterol, HDL, eGFR.