Hypertension and hyperlipidaemia: Random association or cause and effect?

Hypertension and hyper(dys)-lipidaemia are common conditions found in high prevalence in most parts of the developed world. It has not been clear whether they are causally related or associated by chance. A review of the literature shows that the prevalence of hyperlipidaemia is oftern increased in hypertensive patients and vice versa, although there have been several negative reports. Analysis of data from a large survey in Mauritius, where there is a high prevalence of abnormal glucose tolerance, has shown poor association between hypertension, hypercholesterolaemia and hypertriglyceridaemia and no clear relation between blood pressure and lipid levels. The exceptions are patients with non-insulin-dependent diabetes mellitus (NIDDM) where both excess hypertension, raised triglycerides and low HDL-cholesterol are commonly found. Recently 'Syndrome X' has been described in which several conditions (NIDDM and impaired glucose tolerance, hypertension, dyslipidaemia, obesity) occur in clusters presumed to be linked through the common factors of hyperinsulinaemia and insulin resistance. A further link between hypertension and hyperlipidaemia is that both are related to increased sodium-lithium counter-transport activity, but independently. We conclude that hypertension and dyslipidaemia are often found together but this is because of common antecedent risk factors modified by genetic factors, rather than a direct causal association.