BACKGROUND:

The Evans County Studies were initiated as a result of a request from the National Heart Institute in the late 1950's to develop epidemiological studies in areas where significant racial or ethnic differences in cardiovascular disease rates had been observed and where a stable population was available for long-term follow-up. Evans County was in a region of the United States known, at the time, to have the highest total death rates for all causes, of which coronary heart disease and hypertension were major contributors. At that time, Black males and females were known to have four times less coronary heart disease than white males, showed no sex differences for coronary heart disease mortality, and consumed more animal fat and had 50 percent more hypertension.

In 1960, the original Evans County Study cohort was formed when 92 percent of all residents, Black and white, aged 40-74 years and a 50 percent sample of residents aged 15-39 years were given a complete physical examination and a variety of laboratory tests. The major purpose of the original study was to determine factors associated with coronary and related cardiovascular diseases and to explain the low frequency of coronary heart disease in Blacks. Of the initial cohort of 3,102 individuals in 1960, approximately 2,500 were re-examined from 1967 to 1969. Variables studied included serum lipid levels, blood pressure, blood clotting factors, catecholamine levels, physical activity, and social, psychological, and economic factors. Necropsy data were also collected. Follow-up continued on the remaining cohort of approximately 1,900.

Over the years many additional studies were added. The Lipoprotein Phenotyping Study examined which fraction or fractions of high density lipoproteins or low density lipoproteins were related to increased risk for coronary heart disease. The Black-White Neonatal Blood Pressure Study related blood pressure levels during the first year of life to the subsequent development of hypertension and comparing similar groups in other geographical areas to the Evans County group. The Contraceptive Steroids on Blood Pressure Study, funded by the National Institute of Child Health and Human Development, related antecedent characteristics to the development of hypertension or thrombotic disease in the first time oral contraceptive user. The Evans County Health Department also participated Hypertension Detection and Followup Program clinical trial and continued surveillance of the cohort.

Other studies included: the use of defined biracial pedigree cohorts as genetic models to define the possible inheritance of hypertension, hyperlipidemias, coronary heart disease, and thrombosis; maintenance of a collection of frozen sera and food; evaluating new tests to indicate differences in intravascular coagulation between racial and social class groups as related to physical activity, social mobility, and dietary deficiency; studies of the possible relationship to hypertension of dietary sodium-potassium and calcium and selenium intake.

DESIGN NARRATIVE:

Follow-up of the original Evans County Study cohort was achieved by contacting each member annually by mail, telephone, or personal visit, weekly surveys of all admissions at the Evans Memorial Hospital and Statesboro Hospital; survey of daily obituaries in the local newspapers. In the event of a death, autopsy reports and hospital records were obtained. Twice a year teams of consulting neurologists and cardiologists visited Evans County to examine all suspected surviving cases of stroke, transient ischemic attack, myocardial infarction, and angina pectoris. Home visits were conducted for patients who did not visit the medical facility.