Background: Whether concentrations of vitamin D are related to mortality remains unresolved. Our objective was to examine the relationship between serum concentrations of 25-hydroxyvitamin D and all-cause mortality in a national sample of US adults.
Methods: We used data from the National Health and Nutrition Examination Survey Mortality Study from 2001 to 2004 with mortality compiled through 2006. Mortality status was established through a match to the National Death Index.
Results: Of the 7531 participants, 347 died. Median follow-up was 3.8 years. The mean unadjusted concentrations of vitamin D were 54.1 nmol/l (21.7 ng/ml) among participants who died and 60.7 nmol/l (24.3 ng/ml) among participants who survived (P = 0.002). After adjustment for socio-demographic factors, the hazard ratios (HR) for all-cause mortality were 1.65 [95% confidence interval (CI): 95% CI: 1.13-2.40] for participants with a concentration <50 nmol/l (<20 ng/ml) and 1.02 (95% CI: 0.74-1.41) for participants with a concentration of 50 to <75 nmol/l (20 to <30 ng/ml) compared with participants who had a concentration of ≥ 75 nmol/l (≥ 30 ng/ml). After more extensive adjustment, the HRs were 1.28 (95% CI: 0.86-1.90) and 0.91 (95% CI: 0.63-1.33), respectively. The fully adjusted HR per 10 nmol/l of vitamin D was 0.93 (95% CI: 0.86-1.01). The HRs did not vary by gender (P = 0.80) or among the three major racial or ethnic groups (P = 0.46).
Conclusions: Concentrations of vitamin D were weakly and inversely related to all-cause mortality in this sample of US adults.