Vitamin D, Hypertension, and Ischemic Stroke
An Unresolved Relationship
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See related article, pp 499–507
Hypertension, one of the most common chronic diseases worldwide, is a major risk factor for coronary heart disease, cerebrovascular disease, congestive heart failure, end-stage kidney disease, and peripheral vascular disease and consequently results in major disability and mortality. One of the most dreaded complications of hypertension is ischemic stroke. Efforts for over 4 decades have been directed to identify genes that are causally involved in the pathophysiology of hypertension and those that constitute genetically determined risk factors for the development of hypertension and its complications. Can the factors, genetic or otherwise, predisposing to hypertension-related ischemic stroke be identified and can a preventive strategy be derived, based on such information?
It has long been suggested that a low plasma vitamin D level is one of the factors that may be associated with hypertension and ischemic stroke. This notion comes from biological studies in animals and observational studies in humans that relate low active vitamin D levels to the renin–angiotensin system and to arterial wall thickness or stiffness.1–6 Since then, multiple observational studies have tried to demonstrate an inverse correlation between plasma vitamin D levels and hypertension. However, a recent systematic review and meta-analysis of randomized controlled trials on the effect of vitamin D supplementation on blood pressure failed to show that vitamin D supplementation effectively lowers blood pressure,7 casting doubt on the clinical relevance of such correlation. The question nonetheless remains whether there is a real causal relationship between low vitamin D levels and ischemic stroke that is associated with hypertension.
In the current issue of Hypertension, Afzal and Nordestgaard8 approached the problem by asking whether lifelong exposure to low vitamin D level in a native Danish population is indeed a risk factor for high blood pressure on the one …