Hypertension and Stroke in Racial/Ethnic Groups

Abstract

The impact of hypertension is a major contributor to the largely uncontrolled, global disease burden across all racial/ethnic groups. African-Americans have a higher incidence and prevalence of hypertension compared with Caucasians. End-organ manifestations continue to be multi-factorial and have been closely associated with salt sensitivity, obesity, and overactivity of the sympathetic nervous system as well as environmental influences. Despite the advances in the treatment of hypertension, there continues to be a disproportionate burden among racial and ethnic minorities. There is compelling evidence that African-Americans are more susceptible to increased salt load compared to Caucasians, resulting from alterations in kidney function that requires higher arterial pressure to maintain steady-state, causing a shift to the right of the pressure–naturesis curve. In molecular genetic studies on salt sensitivity, several molecular variants have been identified by single strand nucleotides polymorphisms to be more exclusive in blacks than in whites. As a result of having sympathetic overactivity from obesity, there is a compensatory mechanism to burn fat and decrease weight gain, but in exchange for an increased sympathetic discharge to the peripheral vasculature which may predispose on to hypertension.

The African American Heart Failure Trial (A-HeFT) suggested that African-Americans with congestive heart failure demonstrated improvement in morbidity and mortality when added to a fixed-combination therapy of isosorbide dinitrate and hydralazine. This study also supports the implications of a nitric oxide deficiency contribution to a higher cardiovascular burden in African-Americans. The Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) was also one of the first to compare the effectiveness of different classes of antihypertensive therapy; a calcium channel blocker (amlodipine), ACE inhibitor (lisinopril), or an alpha-blocker (doxazosin) were individually compared to a diuretic (chlorthalidone) to reduce fatal or non-fatal coronary heart disease on a diverse population (40,386 study participants) with sufficient power to analyze ethnic groups, especially blacks. The African-American Study of Kidney Disease (AASK) examined the effect of aggressive blood pressure control on progression of renal failure in 1094 African-Americans. One of the largest cohort studies addressing African-Americans and lifestyle modification occurred in the Dietary Approach to Stop Hypertension (DASH) designed to assess the effects of dietary pattern on blood pressure. The Heart and Stroke Statistical Update 2007 states that 70 million people experience a new or recurrent stroke each year. African-Americans may be prone to a higher risk of lacunars infarctions and large artery intracranial occlusive disease, whereas whites may be prone to cerebral embolism, and transient ischemic attack.