Low Dietary Vitamin D in Mid-Life Predicts Total Mortality in Men with Hypertension: The Honolulu Heart Program

Abstract

Background: Vitamin D deficiency was associated with total mortality in previous epidemiological studies. Little is known about the effects of dietary vitamin D intake on mortality. We examined the association between mid-life dietary vitamin D intake and 45-year total mortality. Methods: The Honolulu Heart Program is a longitudinal cohort study of 8006 Japanese American men in Hawaii aged 45 to 68 at baseline (1965–1968). Mid-life dietary vitamin D intake was calculated from 24-hour dietary recall using Nutritionist IV v3 software. We divided subjects into quartiles of dietary vitamin D. Total mortality data were available over 45 years through 2010. Results: Age-adjusted total mortality rates were higher in the lower quartiles of dietary vitamin D intake compared to the highest (p for trend = 0.011). Using Cox regression, low dietary vitamin D was significantly associated with total mortality; quartile (Q) 1 hazard ratio (HR) = 1.14, 95% confidence interval (95% CI) = 1.07–1.22, p < 0.001; Q2 HR = 1.11, 95% CI = 1.04–1.18, p = 0.002; and Q3 HR = 1.08, 95% CI = 1.01–1.15, p = 0.027; Q4 = reference. After adjusting for age, kilocalories, cardiovascular risk factors, and prevalent chronic diseases, only Q2 remained significant (HR = 1.08, 95% CI = 1.00–1.15, p = 0.037). Among hypertensive subjects only, those in the lower 2 quartiles had higher total mortality; Q1 HR = 1.12, 95% CI = 1.01–1.25, p = 0.039, and Q2 HR = 1.13, 95% CI = 1.02–1.26, p = 0.025, compared to Q4. There was no significant relationship in subjects without hypertension. Conclusions: Low dietary vitamin D intake in mid-life was a weak predictor of total mortality over 45 years of follow-up. We found a significant association between low dietary vitamin D intake and higher total mortality only among hypertensive subjects. Vitamin D may have cardioprotective effects.