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Vitamin D deficiency associated with increased risk for CVD
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People with low levels of vitamin D were at twice the risk for cardiovascular events, including myocardial infarction, heart failure or stroke during the next five years compared with those with higher levels of vitamin D, according to results from a recent study.
The researchers analyzed data from 1,739 participants without prior CVD (55% women) from the Framingham Offspring Study. The mean age of participants was 59 years, and all participants were white.
During an average of 5.4 years follow-up, 120 participants had a first cardiovascular event, according to the researchers.
Participants with 25-dihydroxyvitamin D levels ,15 ng/mL had an adjusted hazard ratio of 1.62 (95% CI, 1.11-2.36) for cardiovascular events vs. participants with 25-(OH)D levels >15 ng/mL. Participants with hypertension had a hazard ratio of 2.13 (95% CI, 1.30-3.48), and participants without hypertension had a hazard ratio of 1.04 (95% CI, 0.55-1.96).
Cardiovascular risk was increased in participants with levels of 25-(OH)D 10 ng/mL to ,15 ng/mL (HR=1.53; 95% CI, 1.00-2.36) and in participants with levels ,10 ng/mL (HR=1.80; 95% CI, 1.05-3.08). – by Christen Haigh
Circulation. 2008;doi: 10.1161/CIRCULATIONAHA.107.706127.
Although participants were randomly assigned, there seem to be some imbalances by chance between the calcium and placebo groups with a slightly higher percentage of hypertension, current and former smokers, previous ischemic heart disease, previous stroke, total and LDL cholesterol and dyslipidemia in the calcium arm. This may have influenced the higher outcomes seen in the calcium arm. There were no P values provided to determine if these mild differences between groups at baseline were statistically significant. The researchers also did not report serum vitamin D levels, except to say they excluded those with very severe vitamin D deficiency (less than 25 nmol/L). This population group is entirely from New Zealand, which is closer to the equator than the northern parts of this country. It is possible that this population may have adequate or perhaps even high levels of serum vitamin D. Calcium plus high levels of vitamin D could theoretically lead to vascular calcifications similar to animal models. Although I still believe vitamin D is important and beneficial for cardiovascular health, supplementation with calcium alone (without vitamin D) may not be beneficial for cardiovascular health. A recent meta-analysis of 18 clinical trials suggested that vitamin D supplementation is associated with reduced mortality. This is a thought-provoking study, and further work should be done in this area to confirm.
– Erin Donnelly Michos, MD
Postdoctoral Fellow, Johns Hopkins Hospital