Association Among Vitamin D Supplementation, Serum 25(OH)D Concentrations, and Mortality Risk: A Prospective Cohort Study Using NHANES 2007-2018 Data.

Background: To determine the associations among self-reported vitamin D (VD) supplementation, measured serum 25-hydroxyvitamin D (25[OH]D) concentrations, and all-cause and cause-specific mortality risks.

Methods: Self-reported VD supplementation, serum 25(OH)D concentration, and all-cause and cause-specific mortality data from the National Health and Nutrition Examination Survey 2007-2018 were examined for 10,793 adults ≥20 years from the United States. VD dosage was categorized as <800 or ≥800 IU/d. The mortality status and causes of mortality up to 2019 were determined using the National Death Index. The relationships among VD, 25(OH)D levels, and mortality were analyzed using Cox regression before and after propensity score matching (PSM).

Results: Over a median of 6.6 years, 915 deaths were recorded, 230 because of cardiovascular disease (CVD), 240 because of cancer, and 445 because of other specific causes. Mortality risk did not differ between VD <800 IU/d and ≥800 IU/d before or after PSM. However, serum 25(OH)D concentrations were statistically different before and after PSM. The upper 2 quartiles of 25(OH)D levels were associated with lower all-cause mortality, and the fourth quartile was associated with reduced other-specific mortality before and after PSM. No correlation was found between the 25(OH)D concentration and CVD- or cancer-specific mortality after PSM. The inverse 25(OH)D-mortality relationship was consistent across subgroups.

Conclusions: Based on this large cohort study, higher 25(OH)D levels are robustly associated with reduced all-cause and other specific mortality but not CVD- or cancer-specific mortality. These findings support the benefits of maintaining adequate VD status for longevity. Further research is required to elucidate these mechanisms and define the optimal VD concentration to reduce mortality. These results underscore the importance of public health strategies for preventing VD deficiency.