Abstract:
OBJECTIVES: To evaluate the association between serum 25-hydroxyvitamin D (25(OH)D) levels and mortality in a representative U.S. sample of older adults. DESIGN: Prospective cohort from the Third National Health and Nutrition Examination Survey (NHANES III) and linked mortality files. SETTING: Noninstitutionalized U.S. civilian population. PARTICIPANTS: Three thousand four hundred eight NHANES III participants aged 65 and older enrolled from 1988 to 1994 and followed for mortality through 2000. MEASUREMENTS: Primary exposure was serum 25(OH)D level at enrollment. Primary and secondary outcomes were all-cause and cardiovascular disease (CVD) mortality, respectively. RESULTS: During the median 7.3 years of follow-up, there were 1,493 (44%) deaths, including 767 CVD-related deaths. Median 25(OH)D level was 66 nmol/L. Adjusting for demographics, season, and cardiovascular risk factors, baseline 25(OH)D levels were inversely associated with allcause mortality risk (adjusted hazard ratio (HR)50.95, 95% confidence interval (CI)50.92–0.98, per 10 nmol/L 25[OH]D). Compared with subjects with 25(OH)D levels of 100 nmol/L or higher, the adjusted HR for subjects with levels less than 25.0 nmol/L was 1.83 (95% CI51.14– 2.94) and for levels of 25.0 to 49.9 nmol/L was 1.47 (95% CI51.09–1.97). The association appeared stronger for CVD mortality (adjusted HR52.36, 95% CI51.17–4.75, for subjects with 25[OH]D levelso25.0 nmol/L vs those 100.0 nmol/L) than for non-CVD mortality (adjusted HR51.42, 95% CI50.73–2.79, for subjects with 25[OH]D levelso25.0 nmol/L vs those 100.0 nmol/L). CONCLUSION: In noninstitutionalized older adults, a group at high risk for all-cause mortality, serum 25(OH)D levels had an independent, inverse association with CVD and all-cause mortality. Randomized controlled trials of vitamin D supplementation in older adults are warranted to determine whether this association is causal and reversible.
