Low Dietary Vitamin D Predicts 34-year Incident Stroke: the Honolulu Heart Program

Background And Purpose: Vitamin D deficiency has been reported to contribute to the risk of cardiovascular disease, especially stroke. We examined the relationship between dietary vitamin D intake and 34-year incident stroke.

Methods: The Honolulu Heart Program is a prospective population-based cohort study of 8006 Japanese-American men in Hawaii who were 45 to 68 years old at the baseline examination in 1965 to 1968. Dietary vitamin D intake was calculated using the Nutritionist IV Version 3 software from a 24-hour dietary recall. Subjects with prevalent stroke were excluded, leaving 7385 men followed through 1999 for incident stroke. Subjects were divided into quartiles of dietary vitamin D for analyses.

Results: During 34 years of follow-up, 960 subjects developed stroke. Age-adjusted rates of incident stroke were significantly higher in the lowest dietary vitamin D quartile compared with the highest (all stroke: 6.38 versus 5.14 per 1000 person-years follow-up, P=0.030; thromboembolic stroke: 4.36 versus 3.30, P=0.033). Using Cox regression, adjusting for age, total kilocalories, body mass index, hypertension, diabetes mellitus, pack-years smoking, physical activity index, serum cholesterol, and alcohol intake, those in the lowest quartile had a significantly increased risk of incident stroke (all stroke hazard ratio, 1.22; 95% CI, 1.01-1.47; P=0.038; thromboembolic stroke hazard ratio, 1.27; 95% CI, 1.01-1.59; P=0.044) with the highest as the reference. We found no significant associations between dietary vitamin D and hemorrhagic stroke.

Conclusions: Low dietary vitamin D intake was an independent risk factor for 34-year incidence of all stroke and thromboembolic stroke in Japanese-American men. Additional research is needed on vitamin D supplementation to prevent stroke.