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The aims of the Strong Heart Family Study are to clarify the genetic determinants of cardiovascular disease (CVD) risk in American Indians and to map and identify genes for CVD susceptibility. The authors describe the design of the Strong Heart Family Study (conducted between 1998 and 1999) and evaluate the heritabilities of CVD risk factors in American Indians from this study. In the first phase of the study, approximately 950 individuals, aged 18 years or more, in 32 extended families, were examined. The examination consisted of a personal interview, physical examination, laboratory tests, and an ultrasound examination of the carotid arteries. The phenotypes measured during the physical examination included anthropometry, lipoproteins, blood pressure, glycemic status, and clotting factors. Heritabilities for CVD risk factor phenotypes were estimated using a variance component approach and the program SOLAR. After accounting for the effects of covariates, the authors detected significant heritabilities for many CVD risk factor phenotypes (e.g., high density lipoprotein cholesterol (heritability = 0.50) and diastolic blood pressure (heritability = 0.34)). These results suggest that heredity explains a substantial proportion of the variability of CVD risk factors and that these heritabilities are large enough to warrant a search for major risk factor genes. [ABSTRACT FROM AUTHOR]

Although coronary heart disease (CHD) is currently the leading cause of death among American Indians, information on the prevalence of CHD and its association with known cardiovascular risk factors is limited. The Strong Heart Study was initiated in 1988 to quantify cardiovascular disease and its risk factors among three geographically diverse groups of American Indians. Members of 13 Indian communities in Arizona, Oklahoma, and South and North Dakota between 45 and 74 years of age underwent a physical examination that included medical history; an electrocardiogram; anthropometric and blood pressure measurements; an oral glucose tolerance test; and measurements of fasting plasma lipoproteins, fibrinogen, insulin, hemoglobin A1c, and urinary albumin. Prevalence rates of definite myocardial infarction and definite CHD were higher in men than in women at all three centers (p < 0.0001) and higher in those with diabetes mellitus (p = 0.002 in men and p = 0.0003 in women). Diabetes was associated with relatively higher prevalence rates of myocardial infarction (diabetic:nondiabetic prevalence ratio = 3.8 vs. 1.9) and CHD (prevalence ratio = 4.6 vs. 1.8) in women than in men. Prevalence rates of heart disease were lowest in the communities in Arizona; prevalence rates were similar in Oklahoma and South Dakota/North Dakota and were two- to threefold higher than those in Arizona. By logistic regression, prevalent CHD among American Indians was significantly and independently related to age, diabetes, hypertension, albuminuria, percentage of body fat, smoking, high concentrations of plasma insulin, and low concentrations of high density lipoprotein cholesterol. In contrast to reports from other non-Indian populations, diabetes was the strongest risk factor. The lower prevalence of CHD among Indians in Arizona is distinctive in view of their higher rates of diabetes, obesity, hypertension, and albuminuria, but it may be partly related to their low frequency of smoking and their low concentrations of total and low density lipoprotein cholesterol. These findings from the initial Strong Heart Study examination emphasize the importance of diabetes and its associated variables as risk factors for CHD in Native American populations.