Risk Factors for Coronary Heart Disease in African American Women

American Journal of Epidemiology Copyright © 1999 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved Vol.150, No...
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American Journal of Epidemiology Copyright © 1999 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved

Vol.150, No. 9 Printed in U.S.A.

ORIGINAL CONTRIBUTIONS

Risk Factors for Coronary Heart Disease in African American Women

Lynn Rosenberg,1 Julie R. Palmer,1 R. Sowmya Rao,1 and Lucile L. Adams-Campbell2 There have been few studies of risk factors for coronary heart disease in African American women. The authors investigated factors associated with prevalent coronary heart disease in data provided by participants in the Black Women's Health Study. In 1995, 64,530 US Black women aged 21-69 years completed postal health questionnaires. The 352 women who reported having had a heart attack (cases) were frequency matched 5:1 on age with 1,760 women who had not (controls); medical record review for 35 cases indicated that two-thirds had had a heart attack and the remainder had other coronary heart disease. Odds ratios, obtained from multiple logistic regression analyses, were significantly elevated for cigarette smoking, drug-treated hypertension, drugtreated diabetes mellitus, elevated cholesterol level, and history of heart attack in a parent. High body mass index (kg/m2) was associated with coronary heart disease in the absence of control for hypertension, diabetes mellitus, and elevated cholesterol but not when they were controlled, suggesting that obesity may influence risk as a result of its effects on blood pressure, glucose tolerance, and cholesterol levels. Odds ratios increased with increasing parity and with decreasing age at first birth. These data suggest that important risk factors for coronary heart disease are similar in Black women and White women. Am J Epidemiol 1999;150:904-9. blacks; coronary disease; myocardial infarction; risk factors; women

In the United States, the leading cause of death in Black persons, and the greatest contributor to their excess mortality in relation to White persons, is cardiovascular disease, of which coronary heart disease is the leading component (1-7). Although mortality from coronary heart disease has declined among Black men and women, the rate of decline has been lower than that among White men and women (8). Risk factors for coronary heart disease have been studied extensively in men and in White women but not in African American women (9, 10). Here we report findings from the first case-control study of risk factors for coronary heart disease in Black women, using baseline data collected from the 64,530 participants in the Black Women's Health Study.

MATERIALS AND METHODS Data collection

The Black Women's Health Study began in 1995, when 445,000 questionnaires were mailed to subscribers to Essence magazine, whose readership consists largely of African American women, and to members of several professional organizations of African American women (11). Completed questionnaires were returned by 70,753 women. Respondents younger than age 21 years or older than age 69 years were excluded, leaving 64,530 women aged 21-69 years. The median age of respondents was 38 years, and the largest numbers were from California, Georgia, Illinois, Indiana, Louisiana, Maryland, Massachusetts, Michigan, New Jersey, New York, South Carolina, Virginia, and the District of Columbia. Virtually all participants had had contact with the medical care system in the previous 2 years: 96.0 percent had seen a physician, and 96.6 percent had had their blood pressure checked. The questionnaire included items on demographic characteristics, reproductive history, medical history, and habits such as cigarette smoking. The women were asked if they had ever had any of a list of medical conditions, including heart attack, high blood pressure, diabetes, and high cholesterol. We plan to conduct a

Received for publication September 28, 1998, and accepted for publication March 4, 1999. Abbreviations: Cl, confidence interval; OR, odds ratio. 1 Slone Epidemiology Unit, Boston University School of Medicine, Brookline, MA. 2 Howard University Cancer Center, Howard University College of Medicine, Washington, DC. Reprint requests to Dr. Lynn Rosenberg, Slone Epidemiology Unit, Boston University School of Medicine, 1371 Beacon Street, Brookline, MA 02446-4955. 904

Coronary Heart Disease in African American Women

long-term cohort study to follow the participants for the occurrence of illness. This report is based on casecontrol analyses of the prevalence data reported in the 1995 baseline questionnaire. Cases and controls

Potential cases of coronary heart disease comprised 352 women who reported having had a heart attack and who had not experienced a stroke or a blood clot in the legs or lungs. We obtained hospital records for 35 of the women; for 23, the discharge summary or other part of the medical record showed evidence for a myocardial infarction (66 percent). Five of the remaining 12 women had been treated for congestive heart failure, 5 for unstable angina, and 2 for other cardiovascular diagnoses. The 352 cases were frequency matched 5:1 in 5-year age groups with randomly selected participants who did not report a heart attack, stroke, or clot in the legs or lungs, for a total of 1,760 controls. Data analysis

Unconditional multiple logistic regression analyses were used to estimate odds ratios for the factors under consideration (12). Terms for age, years of education, cigarette smoking, hypertension, diabetes mellitus, elevated cholesterol level, height, history of heart attack in a parent, age at menarche, parity, and age at first birth were included in all the regressions, unless otherwise noted. Hypertension was defined as a positive history of high blood pressure together with use of an antihypertensive or diuretic drug. Diabetes mellitus was defined as a positive history of diabetes together with use of insulin or an oral antidiabetic drug. RESULTS

As shown in table 1, the prevalence of reported coronary heart disease increased from 0.04 percent among Black Women's Health Study participants who

TABLE 1. Prevalence of self-reported coronary heart disease, by age, among participants in the Black Women's Health Study, United States, 1995 Age (years)

15 cigarettes per day) and past smoking (OR = 2.0), hypertension (OR = 3.1), diabetes mellitus (OR = 2.2), elevated cholesterol level (OR = 2.9), and having a parent who had a heart attack before age 50 years (OR = 2.7). Body mass index was weakly related to coronary heart disease: the odds ratio for the highest category, >32.3, relative to the lowest, 15 cigarettes/day Hypertension Diabetes meiiitus Elevated cholesterol level Body mass index (kg/mz) 32.3

95% confidence interval

853 536

Reference 2.0

1.4,2.7

42 38

186 106

1.6 2.3

1.1,2.5 1.4, 3.7

186

422

3.1

2.4, 4.2

59

86

2.2

1.4, 3.7 2.2, 3.9

174

439

2.9

24 38

226 240 304 535 379

Reference 1.4 1.3 1.5 1.4

0.7, 2.5 0.8, 2.4 0.9, 2.6 0.8, 2.5

169 91 53

1,082 329

Reference 1.4 2.7

1.0, 1.9 1.8,4.1

10 8 64 82 91 60 23

36 55 294 450 454 282 132

115

107

Height (inches) 69

Odds ratio*

107 143

52

History of heart attack in a parent No Yes: at age 50 years or older Yes: before age 50 years

Controls

106

1.3 0.8

1.3 Reference 1.0 1.4 0.9

0.6, 3.1 0.3, 1.8 0.9, 1.9

0.7, 1.5 0.9, 2.1 0.5, 1.6

* Odds ratios were estimated from logistic regression equations that included terms for all factors in the table and for age, years of education, age at menarche, parity, and age at first birth.

TABLE 4. Odds ratios for coronary heart disease, by body mass index without control for hypertension, diabetes meiiitus, and elevated cholesterol level, for participants in the Black Women's Health Study, United States, 1995 Body mass index (kg/m2)

32.3

Cases

Controls

Odds ratio*

24 38 52 115 107

226 240 304 535 379

Reference 1.5 1.5 1.9 2.3

95% confidence interval

0.9, 2.7 0.9, 2.6 1.2,3.1 1.4, 3.8

* Odds ratios were estimated from logistic regression equations that included terms for body mass index, age, years of education, cigarette smoking, history of heart attack in a parent, height, age at menarche, parity, and age at first birth.

index of >32.3 relative to 16 years, relative to the lowest,

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