In the second post on vitamin D and CV disease (again largely summarizing this excellent review in Nature Reviews Nephrology), we look at the epidemiological evidence for the association of low vitamin D levels and CVD.
1. Hypertension: Data from NHANES showed that there is an inverse relationship between vitamin D levels and hypertension after full covariate adjustment. Subsequently, data from the Nurses Health Study revealed that low baseline vitamin D levels were associated with an increased risk of incident hypertension. In patients with established hypertension, low levels of vitamin D were associated with an increased risk of CV and all-cause mortality. 2. CV Morbidity and Mortality: Multiple large cohort studies have demonstrated a relationship between low vitamin D levels and CV mortality after controlling for traditional risk factors in a wide variety of populations including Europeans and African-Americans. Data from the Framingham Heart Study suggest that a low level of vitamin D was associated with a HR of 1.62 for incident cardiovascular events after about 6 years follow-up. 3. Chronic Kidney Disease: In patients with chronic kidney disease, there is a U-shaped association between vitamin D levels and CV events. However, this relationship is attenuated after adjustment for baseline GFR suggesting that the primary portion of this risk is related to the severity of renal disease (which may be the cause of the vitamin D deficiency). Low levels of vitamin D have been associated with an increased risk of mortality in dialysis patients while also being a predictor of progression to ESRD. 3. Stroke: Low levels of vitamin D have been associated with an increased risk of ischemic stroke in participants from the Nurses Health Study.
Again, it is important to point out that all of these associations do not prove causality and that there is likely a strong lifestyle or other biologic component in these associations that is not being accounted for. Next we'll look at the clinical trials of vitamin D and CVD prevention.