Oscar Go

Rising Tide of Cardiovascular Disease in American Indians The Strong Heart Study

BACKGROUND Although cardiovascular disease (CVD) used to be rare among American Indians, Indian Health Service data suggest that CVD mortality rates vary greatly among American Indian communities and appear to be increasing. The Strong Heart Study was initiated to investigate CVD and its risk factors in American Indians in 13 communities in Arizona, Oklahoma, and South/North Dakota. METHODS AND RESULTS A total of 4549 participants (1846 men and 2703 women 45 to 74 years old) who were seen at the baseline (1989 to 1991) examination were subjected to surveillance (average 4.2 years, 1991 to 1995), and 88% of those remaining alive underwent a second examination (1993 to 1995). The medical records of all participants were exhaustively reviewed to ascertain nonfatal cardiovascular events that occurred since the baseline examination or to definitively determine cause of death. CVD morbidity and mortality rates were higher in men than in women and were similar in the 3 geographic areas. Coronary heart disease (CHD) incidence rates among American Indian men and women were almost 2-fold higher than those in the Atherosclerosis Risk in Communities Study. Significant independent predictors of CVD in women were diabetes, age, obesity (inverse), LDL cholesterol, albuminuria, triglycerides, and hypertension. In men, diabetes, age, LDL cholesterol, albuminuria, and hypertension were independent predictors of CVD. CONCLUSIONS At present, CHD rates in American Indians exceed rates in other US populations and may more often be fatal. Unlike other ethnic groups, American Indians appear to have an increasing incidence of CHD, possibly related to the high prevalence of diabetes. In the general US population, the rising prevalence of obesity and diabetes may reverse the decline in CVD death rates. Therefore, aggressive programs to control diabetes and its risk factors are needed.

Adverse Effects of Diabetes on Multiple Cardiovascular Disease Risk Factors in Women: The Strong Heart Study

OBJECTIVE Many studies have shown that diabetes increases the risk of cardiovascular disease (CVD) in women to a greater extent than in men. One explanation could be that diabetes has more adverse effects on CVD risk factors in women than in men. We compared diabetes-associated differences in CVD risk factors in men and women in the Strong Heart Study, a population-based study of CVD and its risk factors in American Indians. RESEARCH DESIGN AND METHODS A total of 1,846 men and 2,703 women between the ages of 45 and 74 years from 13 American Indian communities in three geographic areas underwent an examination that included a medical history; an electrocardiogram; anthropometric and blood pressure measurements; an oral glucose tolerance test; and measurements of fasting plasma lipoproteins, fibrinogen, insulin, HbA1c, and urinary albumin. RESULTS Statistically significantly greater adverse differences in those with diabetes versus those without diabetes were observed in women than in men for waist-to-hip ratio, HDL cholesterol, apolipoprotein (apo)B, apoA1, fibrinogen, and LDL size. In multiple linear regression models adjusting for age, center, sex, and diabetes, the diabetes by sex interaction terms were statistically significant for waist-to-hip ratio, LDL cholesterol, HDL cholesterol, apoB, apoA1, fibrinogen, and LDL size. CONCLUSIONS Compared with diabetes-associated differences in men, diabetes in women was related to greater adverse differences in levels of several CVD risk factors. Although the magnitude of the individual diabetes-related differences between men and women was not large, the combined effects of these risk factor differences in diabetic women may be substantial. The apparent greater negative impact of diabetes on CVD risk factors in women may explain, in part, the greater risk for CVD in diabetic women.

LDL Cholesterol as a Strong Predictor of Coronary Heart Disease in Diabetic Individuals With Insulin Resistance and Low LDL The Strong Heart Study

Diabetes has been shown to increase the risk of coronary heart disease in all populations studied. However, there is a lack of information on the relative importance of diabetes-associated risk factors for cardiovascular disease (CVD), especially the role of lipid levels, because low density lipoprotein (LDL) cholesterol often is not elevated in diabetic individuals. The objective of this analysis was to evaluate CVD risk factors in a large cohort of diabetic individuals and to compare the importance of dyslipidemia (ie, elevated triglycerides and low levels of high density lipoprotein [HDL] cholesterol) and LDL cholesterol in determining CVD risk in diabetic individuals. The Strong Heart Study assesses coronary heart disease and its risk factors in American Indians in Arizona, Oklahoma, and South/North Dakota. The baseline clinical examinations (July 1989 to January 1992) consisted of a personal interview, physical examination, and drawing of blood samples for 4549 study participants (2034 with diabetes), 45 to 74 years of age. Follow-up averaged 4.8 years. Fatal and nonfatal CVD events were confirmed by standardized record review. Participants with diabetes, compared with those with normal glucose tolerance, had lower LDL cholesterol levels but significantly elevated triglyceride levels, lower HDL cholesterol levels, and smaller LDL particle size. Significant independent predictors of CVD in those with diabetes included age, albuminuria, LDL cholesterol, HDL cholesterol (inverse), fibrinogen, and percent body fat (inverse). A 10-mg/dL increase in LDL cholesterol was associated with a 12% increase in CVD risk. Thus, even at concentrations well below the National Cholesterol Education Program target of 130 mg/dL, LDL cholesterol is a strong independent predictor of coronary heart disease in individuals with diabetes, even when components of diabetic dyslipidemia are present. These results support recent recommendations for aggressive control of LDL cholesterol in diabetic individuals, with a target level of <100 mg/dL.

Diabetes and Impaired Glucose Tolerance in Three American Indian Populations Aged 45-74 Years: The Strong Heart Study

OBJECTIVE To estimate prevalence rates of diabetes and impaired glucose tolerance (IGT) in three American Indian populations, using standardized diagnostic criteria, and to assess the association of diabetes with the following selected possible risk factors: age, obesity, family history of diabetes, and amount of Indian ancestry. RESEARCH DESIGN AND METHODS This cross-sectional study involved enrolled members, men and women aged 45-74 years, of 13 American Indian tribes or communities in Arizona, Oklahoma, and South and North Dakota. Eligible participants were invited to the clinic for a personal interview and a physical examination. Diabetes and IGT status were defined by the World Health Organization criteria and were based on fasting plasma glucose and oral glucose tolerance test results. Data on age, family history of diabetes, and amount of Indian ancestry were obtained from the personal interview, and measures of obesity included body mass index, percentage body fat, and waist-to-hip ratio. RESULTS A total of 4,549 eligible participants were examined, and diabetes status was determined for4,304(1,446 in Arizona, 1,449 in Oklahoma, and 1,409 in the Dakotas). In all three centers, diabetes was more prevalent in women than in men. Arizona had the highest age-adjusted rates of diabetes: 65% in men and 72% in women. Diabetes rates in Oklahoma (38% in men and 42% in women) and South and North Dakota (33% in men and 40% in women), although considerably lower than in Arizona, were several times higher than those reported for the U.S. population. Rates of IGT among the three populations (14-17%) were similar to those in the U.S. population. Diabetes rates were positively associated with age, level of obesity, amount of Indian ancestry, and parental diabetes status. CONCLUSIONS Diabetes is found in epidemic proportions in Native American populations. Prevention programs and periodic screening should be implemented among American Indians. Standards of care and intervention have been developed by the Indian Health Service for individuals in whom diabetes is diagnosed. These programs shoula be expanded to include those with IGT to improve glycemie control or to reduce the risk of development of diabetes as well as to reduce the risk of diabetic complications.

Hypertension in Adult American Indians: The Strong Heart Study

Hypertension is a primary risk factor for cardiovascular disease in the United States. Although cardiovascular disease is the leading cause of death among American Indians, the prevalence of hypertension, its awareness and control, and its association with other cardiovascular disease risk factors and physiological variables have not been well studied in this population. The Strong Heart Study is a longitudinal study of cardiovascular disease and its risk factors in American Indians. Participants (2703 women and 1846 men) were members of 13 tribes in central Arizona, southwestern Oklahoma, and regions of South and North Dakota. At least 1500 individuals between 45 and 74 years of age participated from each center in a baseline clinical examination conducted between July 1989 and January 1992. The examination consisted of a personal interview and physical examination that included an oral glucose tolerance test and three consecutive blood pressure measurements. This study reports data from the baseline examination on the prevalence of hypertension and correlates of blood pressure. Results indicated that despite the high frequency of diabetes and obesity, prevalence rates of hypertension in Arizona and Oklahoma were similar to those in the US population in the Third National Health and Nutrition Examination Survey (NHANES III), and rates among South/North Dakota participants were significantly lower (P < .0001). Blood pressure was higher in individuals with diabetes (P < .0001) and was significantly correlated with age (P < .0001) and albuminuria (P < .0001) but only weakly related to obesity. There was no independent relation between blood pressure and insulin. Blood pressure seems to be less affected by obesity and hyperinsulinemia in American Indians compared with other populations. Nevertheless, hypertension should be aggressively treated and controlled in American Indians because it is a known precursor to morbidity and mortality associated with diabetes and cardiovascular disease.

Apolipoprotein E Polymorphism in American Indians and Its Relation to Plasma Lipoproteins and Diabetes The Strong Heart Study

Apo E is an important genetic factor in the development of cardiovascular disease, which is the leading cause of death among American Indians. We investigated the occurrence of the apo E alleles and the relation between apo E polymorphism and blood lipoproteins and apoproteins in members of 13 American Indian communities in three geographic areas. The frequencies of the epsilon 2 alleles in American Indians are significantly lower than those in white Americans, with the lowest frequencies of epsilon 2 in American Indians who reside in Arizona. Levels of LDL cholesterol and apo B were highest in those with epsilon 4 and lowest in those with epsilon 2. Concentrations of HDL cholesterol and apo A-I, however, tended to be lowest in epsilon 4 and highest in epsilon 2. Concentrations of total and VLDL triglycerides were lowest in the epsilon 3 group and higher in groups epsilon 2 and epsilon 4. Differences in concentrations of LDL cholesterol, HDL cholesterol, apo B, and apo A-I with apo E polymorphism were greater in women than in men, and differences in total and VLDL triglyceride concentrations by apo E phenotype were greater in men. Relations of total and VLDL triglycerides with apo E phenotype were stronger in women after menopause. In addition, differences in nearly all lipid and apoprotein concentrations between postmenopausal women and premenopausal women were greater if they had epsilon 2. Relations between apo E phenotype and lipoproteins were seen in individuals with diabetes mellitus as well as in nondiabetics. Apo E was significantly related to glucose control in diabetic women; those with epsilon 3 had higher glucose and hemoglobin A1C concentrations. Our findings show that (1) American Indians have low frequencies of apo epsilon 2; (2) apo E phenotype can influence levels of VLDL, LDL, HDL, apo B, and apo A-I; (3) the associations of apo E polymorphisms with lipid parameters differ between men and women; and (4) the associations in women of apo E polymorphisms with lipid parameters are modified by menopausal status.

Physical activity and lipids and lipoproteins in American Indians ages 45-74

PURPOSE The Strong Heart Study is a study of cardiovascular disease and its risk factors among American Indian men and women aged 45-74 yr representative of 13 communities from Arizona (AZ), Oklahoma (OK), and North/South Dakota (N/SD). This investigation sought to characterize the amount and type of physical activity and to determine the association between activity and lipids in this population. METHODS Total physical activity (occupational plus leisure) was assessed with a validated questionnaire. RESULTS Men and women from OK (21 +/- 19 and 16 +/- 15 h.wk-1; respectively) and N/SD (23 +/- 21 and 17 +/- 17 h.wk-1; respectively) had activity levels that were similar if not lower than the U.S. population with the AZ communities (17 +/- 21 and 10 +/- 14 h.wk-1; respectively) being substantially lower than the other two communities. Total cholesterol (TC), high density lipoprotein cholesterol (HDL-c), and low density lipoprotein cholesterol (LDL-c) levels were lower than the U.S. population. CONCLUSIONS For most of the population (diabetic men and nondiabetic men and women), activity was significantly associated (P < 0.05) with apolipoprotein (apo) AI after controlling for covariates. With levels of activity as low if not lower than the general U.S. population coupled with high prevalence of obesity and diabetes, efforts to increase physical activity in American Indians are warranted. Hopefully these increases in activity will result in favorable lipid changes as well as decreasing the risk of diabetes which is epidemic in these populations.