Differences in Cardiovascular Disease Risk Factors in Black and White Young Adults: Comparisons among Five Communities of the CARDIA and the Bogalusa Heart Studies

Differences in Cardiovascular Disease Risk Factors in Black and White Young Adults: Comparisons among Five Communities of the CARDIA and the Bogalusa Heart Studies KURT J. GREENLUND, PhD, CATARINA I. KIEFE, PhD, MD, SAMUEL S. GIDDING, MD, CORA E. LEWIS, MD, SATHANUR R. SRINIVASAN, PhD, O. DALE WILLIAMS, PhD, AND GERALD S. BERENSON, MD

PURPOSE: To examine community differences in cardiovascular disease (CVD) risk factors among black and white young adults by combining data from two large epidemiologic studies. METHODS: Data are from participants aged 20–31 years in the Coronary Artery Risk Development In Young Adults (CARDIA) study (1987–1988; N 5 4129) and the Bogalusa Heart study (1988–1991; N 5 1884), adjusting for data collection differences prior to analysis. CARDIA includes four urban sites: Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; and Oakland, California. Bogalusa is a semi-rural town in Southeastern Louisiana. CVD risk factors examined were smoking status, body habitus, and blood pressure. RESULTS: In Birmingham and Bogalusa, more white than black women were current smokers; no ethnic differences were observed among men. In Chicago, Minneapolis, and Oakland, more blacks were current smokers than were whites. For all sites, educational level was strongly inversely related to current smoking status; ethnic differences were more apparent among those with up to a high school education. Among white men and women, prevalence of obesity (body mass index . 31.1 kg/m2 in men and 32.3 kg/m2 in women) was greater in Birmingham and Bogalusa than in Chicago, Minneapolis, and Oakland. Mean systolic blood pressures were highest in Bogalusa, and the proportion of black men with elevated blood pressure (> 130/85 mmHg) was higher in Bogalusa and Birmingham. CONCLUSIONS: Community and ethnic differences in CVD risk factors were observed among young adults in two large epidemiologic studies. Further studies may enhance our understanding of the relationship of geographic differences in CVD risk to subsequent disease. Ann Epidemiol 1998;8:22–30.  1998 Elsevier Science Inc. KEY WORDS:

Cardiovascular Disease, Regional Variation, Risk Factors.

INTRODUCTION Regional differences in cardiovascular disease (CVD) mortality and morbidity in the U.S. have been documented by a variety of reports, some based on national data and others from a collection of separate studies (1–7). Rural-urban differences also have been observed (8–11). One consequence is that the southeastern U.S. has been termed the ‘Stroke Belt’ due to its higher stroke mortality rates (12–14). Examination of the geographic variation of disease may help

From the Tulane Center for Cardiovascular Health, Tulane School of Public Health & Tropical Medicine, New Orleans, LA (K.J.G., S.R.S., G.S.B.); Division of Preventive Medicine, University of Alabama at Birmingham, Birmingham, AL (C.I.K., C.E.L., O.D.W.); and the Departments of Pediatrics and Preventive Medicine, Northwestern University Medical School, Chicago, IL (S.S.G.). Address reprint requests to: Kurt J. Greenlund, Ph.D., Division of Adult and Community Health, Centers for Disease Control and Prevention, 4770 Buford Hwy NE, Mailstop K-45, Atlanta, GA 30341-3724. Received February 13, 1997; revised August 11, 1997; accepted August 12, 1997.  1998 Elsevier Science Inc. All rights reserved. 655 Avenue of the Americas, New York, NY 10010

to identify important population, cultural, and environmental factors associated with disease risk (15). Information on geographic variation in the major CVD risk factors and their correlates, especially for age-race-gender specific groups, is not desirably complete. Regional variation has been reported for smoking and tobacco use, especially among men (16), and differences in height and weight have been examined (17, 18). Further, an increased prevalence of hypertension among black women in the southeastern U.S. was observed in the 1976–1980 National Health and Nutrition Examination Survey (NHANES) (14). National Center for Health Statistics data demonstrate consistently higher hypertension-related CVD death rates over time in the Southeast (1). Overall, however, information is lacking on geographic differences in risk factors for CVD which may contribute to the differences in disease and death rates. Comparisons of CVD risk factors derived from reports relative to separate community studies can provide important insight on geographic similarities and differences in 1047-2797/98/$19.00 PII S1047-2797(97)00127-0

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Selected Abbreviations and Acronyms CVD 5 cardiovascular disease CARDIA 5 coronary artery risk development in young adults NHANES 5 National Health and Nutrition Examination Survey BMI 5 body mass index NHIS 5 National Health Interview Survey

disease risk (19). Such comparisons need to properly take into account different procedures and definitions used in the separate studies. For example, Epstein and Eckoff (20) reported substantial blood pressure variation among 48 population groups throughout the world; however, it was not possible to assess how different measurement methodology contributed to these apparent differences. The more recent INTERSALT study, which used common, carefully standardized methods at all data collection sites, provided important international comparisons of blood pressure levels (21). For this report, community differences in CVD risk factors were examined among five sites from two separate studies— the Coronary Artery Risk Development in Young Adults (CARDIA) study and the Bogalusa Heart study—for black and white young adults aged 20–31 years in 1987–88 from CARDIA, and 1988–1991 in the Bogalusa Heart study. The five sites included southern semi-rural and urban communities, two northern (midwestern) urban communities and one western urban community. The two studies utilized similar, but not identical, data collection methods, which were examined and standardized as closely as possible prior to data analysis. This approach allowed common statistical modeling strategies to be undertaken.

METHODS Differences in CVD risk factors among and within the CARDIA and Bogalusa Heart studies were compared after selection of subsamples and variables were redefined to maximize comparability. Smoking status, body habitus, and blood pressure were the main variables of interest. Alcohol consumption, oral contraceptive use, and family history of hypertension were examined as possible covariates. These variables were chosen as risk factors which may be related to regional variability in CVD morbidity and mortality, and based on similarity in data collection methods or ability to standardize the data across the studies. CARDIA is a longitudinal study of the development of coronary artery disease risk factors in young adults (22, 23). For this study, 5115 adults, aged 18–30 years at baseline (1985–86), were recruited from four urban sites (Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; and Oakland, California). The recruitment goal was to include approximately equal numbers of participants by

Greenlund et al. COMMUNITY DIFFERENCES IN CVD RISK FACTORS

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age group (18–24, 25–30 years), education level (up to high school, more than high school), ethnicity (black, white), and gender. Once a subgroup based on gender, race, age, and education was filled, further recruitment ceased. In Birmingham, Chicago, and Minneapolis, participants were randomly recruited, chiefly through telephone contact (doorto-door contact in some areas of Minneapolis), from the total community or from census tract areas. In Oakland, participants were randomly recruited from a health plan membership roster. CARDIA participants were re-examined at two (1987–88), five (1990–91), seven (1992–93), and ten years (1995–96) after the baseline exam. Overall, 51% of eligible persons participated in the CARDIA baseline exam. The Bogalusa Heart study is a community-based, longterm study of the development of CVD beginning in childhood in a semi-rural, biracial (white, black) community in southeastern Louisiana (24). The study has both crosssectional and longitudinal components. Examinations of children aged 5–17 years have been conducted approximately every three to five years since 1973, on new as well as previously examined participants. The racial distribution of the cohorts has reflected that of the community as a whole—approximately 2/3 white and 1/3 black. The longitudinal cohort consists of all persons aged 18 and older who were examined as children in the Bogalusa Heart Study. As children who participated in the study became 18 years of age, they were entered into a registry for longitudinal followup. In 1988–1991, all participants first screened in 1973 at ages 5–14 years were eligible for screening as young adults (ages 18–31 years). Of 3086 persons available for examination, 1930 (62.5%) were screened in the 1988–1991 examination. The Bogalusa Heart study young adult participants were first screened as children aged 5–14 years beginning in 1973, while CARDIA participants were first screened as young adults aged 18–30 years in 1985. Nevertheless, overlapping cohorts of young adults of similar age and examination period could be identified, and data collection methods were similar for a number of key parameters, making meaningful comparisons possible. From CARDIA, the study sample consisted of 4129 persons aged 20–31 years examined in 1987–88. From Bogalusa, the study sample included 1884 persons aged 20–31 years examined in 1988–1991. Smoking Status In CARDIA, current smoking status was derived from selfand interviewer-administered questions with current smoking defined as smoking at least five cigarettes per week for at least three months. In Bogalusa, smoking status was also derived from self-reported questionnaire data, with current smoking defined as smoking at least one cigarette per week. In both studies, the number of cigarettes per day was also

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recorded. For this report, current smokers in Bogalusa were reclassified as those who smoke at least five cigarettes per week. Alcohol Consumption In both studies, alcoholic beverage consumption was ascertained by questionnaire. Whereas past consumption covered only the year preceding the examination for CARDIA, Bogalusa inquired about past consumption without specifying a time interval. Both studies assessed present consumption in terms of current weekly alcohol intake. Although the wording of the questions in the two studies was not the same, it was possible to compute weekly mean alcohol consumption in a generally comparable way, with the number of drinks per week converted to milliliters of alcohol (25). In the Bogalusa study, however, consumption of wine coolers was ascertained while it was not in CARDIA. Oral Contraceptive Use In both studies, women were asked if they currently used oral contraceptives and, if yes, the brand name was recorded. In Bogalusa, the interviewer utilized a booklet containing examples of oral contraceptives to assist in identifying the brand. History of Hypertension For both studies, subjects were asked whether they were currently taking medication for high blood pressure and, if yes, the type of medication was recorded. Subjects were also asked whether their mother or father had high blood pressure. In addition, CARDIA participants were asked whether their siblings had high blood pressure. For this report, family history of hypertension was based only on information about the mother and father.

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with a mercury sphygmomanometer. First, fourth, and fifth Korotkoff sounds were recorded three times by each technician at one minute intervals after an initial five minute rest. Typically, the study has reported the average of six readings as the measure of blood pressure. For this report, the average of the second and third readings was used as the measure of blood pressure, and the fifth Korotkoff sound was used for the diastolic reading. This resulted in the standard CARDIA blood pressure values, and a recalculation of blood pressures in Bogalusa which resulted in an average of 2 mmHg higher systolic reading and 2 mmHg lower diastolic reading than those usually reported for the Bogalusa Heart Study. Participants were classified as having elevated blood pressure if they reported taking hypertension medication or had a systolic blood pressure > 130 mmHg and/or diastolic pressure > 85 mmHg. These cut points correspond to the Fifth Joint National Committee on High Blood Pressure criteria for high normal blood pressure (27) and were used since very few participants exhibited high blood pressure according to the standard definition (28). Statistical Analyses Descriptive characteristics were generated by race and sex within sites. Unadjusted between-site comparisons were performed using one-way analysis of variance and chi-square tests, as appropriate. Within race/sex groups, center differences were assessed by analyses of covariance with blood pressure and BMI as dependent variables, adjusting for age, smoking status, education, alcohol consumption, and BMI (for blood pressure). Among women, oral contraceptive use status was also examined as a covariate. Multiple logistic regression was used to adjust differences in prevalence of elevated blood pressure, severe overweight, and current drinking status for pertinent covariates.

Anthropometry In both studies, height (stationary height boards) and weight (balance beam scales) were measured with subjects dressed in light clothing and without shoes. In Bogalusa, height and weight were measured twice and averaged, while in CARDIA, height and weight each were measured once. Body mass index (BMI, kg/m2) was calculated in both studies. Prevalence of severe overweight was calculated as BMI . 31.1 kg/m2 in men and 32.3 kg/m2 in women (26). Blood Pressure In CARDIA, blood pressure was measured with a Hawksley random-zero sphygmomanometer three times at one minute intervals after an initial five minute rest. First and fifth Korotkoff sounds were recorded for systolic and diastolic readings, respectively. Previous reports from the study have been based on the average of second and third readings. In Bogalusa, blood pressure was measured by two trained technicians

RESULTS Demographic characteristics for the participants from the five sites are shown in Table 1. Two differences between Bogalusa and CARDIA sites are immediately apparent. Bogalusa participants appear slightly younger and have lower educational levels. These apparent differences are likely due to differing selection criteria for the two studies. For example, in CARDIA, educational level was a criterion for selection into the study, with half of the participants required to have greater than a high school education. The Bogalusa sampling plan did not have such a requirement since its participants were enrolled before they were old enough to go beyond high school. Smoking The most striking differences were for smoking prevalence, particularly ethnic differences by center (Table 1). For ex-

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TABLE 1. Selected characteristics, participants aged 20–31 years, the CARDIA study (1987–88) and the Bogalusa Heart study (1988–1991) Bogalusa

Birmingham

Sample Sizes n (%) Black women White women Black men White men Total

348 (18.5) 721 (38.3) 250 (13.3) 565 (30.0) 1884 (100)

299 215 232 226 972

Age (years); mean (SD) Black womena White womena Black menb White mena Totala

25.6 25.6 25.7 26.0 25.7

26.5 27.0 26.4 27.0 26.7

(3.0) (3.1) (3.1) (3.1) (3.1)

(30.8) (22.1) (23.9) (23.3) (100) (3.5) (3.1) (3.5) (3.2) (3.4)

Chicago

Minneapolis

Oakland

256 (28.0) 246 (26.9) 183 (20.0) 228 (25.0) 913 (100)

227 (20.2) 347 (30.8) 232 (20.6) 320 (28.4) 1126 (100)

376 (33.6) 283 (25.3) 255 (22.8) 204 (18.3) 1118 (100)

26.0 27.3 26.3 27.5 26.8

25.8 27.9 25.9 27.8 27.0

26.7 27.3 26.6 27.5 27.0

(3.5) (3.2) (3.6) (2.9) (3.3)

(3.2) (2.8) (3.4) (2.9) (3.2)

(3.4) (3.3) (3.2) (3.2) (3.3)

Education more than high school (%) Black womena White womena Black mena White mena Totala

39.4 50.4 26.4 43.1 43.0

68.5 73.5 59.9 71.1 68.2

59.6 86.2 53.6 82.9 71.4

40.1 71.5 27.7 72.5 56.4

70.5 82.3 67.5 84.6 75.4

Oral contraceptive users (%) Black womenb White womena All womena

35.9 38.7 37.8

42.4 51.9 46.4

29.9 41.1 35.6

29.7 34.4 32.4

36.1 35.2 35.8

Current smoker (%) Black womena White womena Black mena White mena Totala

26.1 37.6 36.1 39.4 35.9

19.7 27.2 32.3 32.3 27.3

30.0 26.1 40.1 19.3 28.3

48.2 29.4 53.0 35.3 39.7

29.2 14.8 29.4 14.9 23.0

Current drinker (%) Black womena White womenb Black men White mena Total*

46.8 61.6 66.4 68.0 61.4

37.3 56.7 64.7 73.8 56.7

32.2 69.5 68.3 80.3 61.5

49.8 56.8 74.6 72.8 63.6

45.2 66.4 63.6 79.1 61.1

Alcohol consumptionc (ml/wk): mean (sd) Black womenb White womena Black men White menb Totala

61.6 53.2 174.6 139.3 100.4

(103.8) (97.4) (248.3) (180.9) (164.7)

71.7 97.4 196.0 152.8 136.0

(76.2) (93.3) (276.3) (165.6) (185.5)

95.4 119.3 199.2 154.5 145.1

(107.2) (147.2) (219.6) (125.4) (159.0)

103.7 103.6 216.2 187.5 158.1

(107.1) (166.7) (240.0) (246.5) (213.0)

86.8 88.6 145.0 131.3 111.7

(105.5) (72.3) (205.4) (131.6) (137.1)

p < 0.005 for differences among centers within race-sex groups. p < 0.05 for differences among centers within race-sex groups. c Current drinkers only. a

b

ample, white women and men reportedly smoked the least of the race-gender groups in Oakland (14.8% among women and 14.9% among men), but had the most in Bogalusa (37.6% among women and 39.4% among men). White women had a greater smoking prevalence than black women in Bogalusa and Birmingham, whereas black women had a greater smoking prevalence in Chicago, Minneapolis, and Oakland. For Bogalusa and Birmingham, there was little or no difference between black and white men in the percentage of current smokers, whereas black men had

a greater smoking prevalence in Chicago, Minneapolis, and Oakland. Ethnic differences in smoking rates were more apparent among those with up to a high school education (Table 2). Among women with up to a high school education, more white women than black women were current smokers in Bogalusa, Birmingham and Chicago, whereas more black women were current smokers in Minneapolis and Oakland. Among women with more than a high school education, more white women smoked than did black women only in

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TABLE 2. Percent current smoking status by educational level, race, sex, and center, participants aged 20–31 years, CARDIA (1987–88) and the Bogalusa Heart study (1988–1991) Education Center

Up to high school

More than high school

p

Bogalusa Black women White women Black men White men Total

31.7 46.0 40.5 51.9 44.1

17.8 29.3 24.6 23.1 25.1

0.004 0.001 0.023 0.001 0.001

Birmingham Black women White women Black men White men Total

28.0 50.9 47.3 56.9 44.2

16.3 18.6 22.3 22.5 19.6

0.020 0.001 0.001 0.001 0.001

Chicago Black women White women Black men White men Total

41.8 73.5 57.1 35.9 50.0

22.0 18.5 25.5 15.9 19.6

0.001 0.001 0.001 0.004 0.001

Minneapolis Black women White women Black men White men Total

55.6 48.5 63.5 55.7 56.9

37.4 21.8 26.6 27.6 26.6

0.007 0.001 0.001 0.001 0.001

Oakland Black women White women Black men White men Total

42.1 34.0 45.0 38.7 41.1

22.4 11.2 20.9 10.1 16.4

0.001 0.001 0.001 0.001 0.001

Bogalusa, while more black women smoked in Minneapolis and Oakland than did white women. Among men with up to a high school education, more white men smoked than did black men in Bogalusa and Birmingham, while the reverse was true in Chicago, Minneapolis, and Oakland. Among men with more than a high school education, more black men were current smokers than were white men only in Chicago and Oakland, with no ethnic differences among men in the other centers.

Bogalusa falling in between (Table 1). Prevalence of oral contraceptive use was statistically different among black and white women in Chicago (p 5 0.02) and Birmingham (p 5 0.05). Anthropometry

No clearly discernible regional trends could be observed in the percentage of current drinkers (Table 1). For each of the five communities, blacks, both men and women, tended to have lower proportions of current drinkers than whites. For women drinkers, Bogalusa had the lowest mean alcohol consumption, but for men, the lowest mean consumption was in Oakland (Table 1).

Few notable differences in mean weight, height, or BMI were observed among the sites (Table 3). In Bogalusa and Birmingham, white women were slightly shorter and white men had a slightly greater BMI compared to white women and men, respectively, in the other centers. For all sites, black women had the greatest BMI. The percentages of severe overweight among black women ranged from 12.8% in Minneapolis to 20.4% in Bogalusa. Among white women and men, the percentages with severe overweight were greater in Bogalusa and Birmingham than in Chicago, Minneapolis, and Oakland.

Oral Contraceptive Use

Blood Pressure

Prevalence of oral contraceptive use was greater in Birmingham than in Chicago, Minneapolis, and Oakland, with

Mean systolic blood pressure was slightly higher in Bogalusa than in the CARDIA sites (Table 4), especially among

Alcohol Intake

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TABLE 3. Anthropometric characteristics, participants aged 20–31 years, CARDIA (1987–88) and the Bogalusa Heart study (1988–1991) Bogalusa

Birmingham

Chicago

Minneapolis

Oakland

Weight (kg); mean (SD) Black women White womena Black men White menb Total

72.3 64.0 79.1 81.1 72.7

Height (cm); mean (SD) Black women White womenb Black men White men Totalb

163.1 163.2 176.1 177.1 169.1

(6.3) (6.3) (6.7) (6.7) (9.3)

163.6 163.4 176.9 177.5 170.0

(7.1) (6.3) (7.3) (6.7) (9.7)

162.7 165.5 177.3 178.1 170.2

(6.6) (5.9) (7.1) (6.9) (9.5)

163.0 165.1 176.2 178.5 170.8

(7.3) (6.5) (6.9) (6.6) (9.5)

164.0 165.2 176.6 177.8 169.7

(6.7) (6.7) (6.8) (7.0) (9.2)

BMI (kg/m2); mean (SD) Black women White womena Black men White menb Totala

27.1 24.0 25.5 25.8 25.3

(7.1) (5.5) (5.5) (4.6) (5.7)

26.7 23.2 25.7 25.5 25.4

(6.9) (5.4) (5.4) (4.2) (5.8)

26.8 23.1 24.9 24.9 24.9

(6.7) (4.2) (4.2) (3.1) (5.0)

25.5 24.2 25.0 24.6 24.8

(6.5) (4.8) (4.2) (3.8) (4.9)

26.7 23.5 25.5 24.4 25.2

(6.8) (4.4) (4.5) (3.5) (5.3)

Severe Overweightc (%) Black women White womena Black men White menb Totalb

(19.8) (14.8) (18.2) (15.7) (18.1)

20.4 9.0 14.1 12.1 12.7

71.5 62.1 80.2 80.2 73.6

(20.2) (15.6) (18.1) (15.0) (19.0)

17.2 7.5 14.7 10.2 12.8

70.6 63.1 78.1 79.0 72.1

(18.0) (11.6) (14.9) (11.4) (15.7)

19.8 3.7 10.1 5.3 9.8

67.8 65.9 77.7 78.3 72.3

(18.2) (14.4) (14.5) (13.9) (16.2)

12.8 6.3 8.6 5.6 7.9

71.8 64.0 79.6 77.1 72.6

(19.1) (12.5) (15.4) (12.3) (16.6)

18.2 5.4 10.4 4.9 10.7

p < 0.05 for differences among centers within race-sex groups. p < 0.005 for differences among centers within race-sex groups. c Severe overwight is defined as a body mass index greater than 31.1 kg/m2 in men and 32.3 kg/m2 in women (see reference 25). a

b

women. Systolic blood pressures were lowest in Oakland. However, diastolic blood pressure was about the same or slightly lower in Bogalusa. For all sites, men had higher blood pressures compared with women. Except in Oakland, black men and women tended to have higher mean systolic blood pressures than white men and women, respectively. Among both black men and white men, prevalence of subjects taking antihypertensive medication was greater in Bogalusa and Birmingham compared with the other sites (though the numbers are small and must thus be interpreted with caution). Prevalence of elevated blood pressure also tended to be greater among men in Bogalusa and Birmingham. Family history of hypertension was also greater among blacks than whites within sites. Women, both black and white, but not men, tended to report more family history of hypertension in Bogalusa and Birmingham than in the other three sites. Multivariable Analyses Adjustment of BMI and blood pressure for other covariates (Table 5) resulted in similar results to those reported above. White men still tended to have slightly higher mean BMI levels in Bogalusa and Birmingham, while a significant center difference among white women disappeared after adjusting for other factors. Adjusted systolic blood pressure

tended to be highest in Bogalusa and lowest in Oakland. Among women, adjustment for oral contraceptive use did not change the results (data not shown. Adjustment of severe overweight, elevated blood pressure or current drinker status for appropriate covariates also did not change our results, except that a center difference of severe overweight among white women, as with BMI, was not statistically significant after further adjustment.

DISCUSSION Comparing and contrasting risk factor levels and disease rates by geographic area can enhance our understanding of the etiology and pathogenesis of CVD (29). Important differences in CVD mortality rates among regions of the U.S. have been the object of much curiosity and research for many years. Regional differences in CVD have been observed in other nations as well (30–35). Fewer studies have examined geographic differences in the major CVD risk factors and their correlates, especially for age-race-sex groups. Among people aged 18–44 years in the National Health Interview Survey (NHIS) (17), the percentage of persons 20% or more over ideal body weight was greater among men and women in the South compared

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TABLE 4. Blood pressure characteristics, participants aged 20–31 years, CARDIA (1987–88) and the Bogalusa Heart study (1988–1991) Bogalusa

Birmingham

Chicago

Minneapolis

Oakland

Systolic blood pressure (mmHg); mean (SD) Black womena White womena Black mena White mena Totala

110.6 107.6 116.9 114.6 111.5

(10.3) (9.5) (12.5) (10.3) (10.9)

106.3 102.0 115.4 112.2 108.9

(9.1) (8.7) (10.8) (9.2) (10.7)

106.2 101.8 115.3 111.5 108.2

(9.5) (8.7) (10.4) (9.8) (10.8)

106.1 (10.1) 104.5 (9.1) 115.4 (10.4) 112.5 (8.9) 109.3 (10.5)

104.1 99.3 110.1 110.1 105.3

(10.1) (8.9) (9.4) (10.0) (10.6)

Diastolic blood pressure (mmHg); mean (SD) Black womena White womenb Black mena White mena Totala

63.6 63.4 67.3 66.6 65.9

(10.7) (9.3) (12.4) (9.7) (10.3)

67.7 65.2 73.4 71.3 69.4

(9.1) (7.8) (9.5) (9.2) (9.4)

66.3 64.0 68.8 68.9 66.8

(9.6) (9.1) (11.0) (8.6) (9.7)

66.3 64.9 68.7 68.3 66.9

64.3 63.6 69.2 68.9 66.1

(10.7) (8.6) (8.7) (8.6) (9.7)

(9.6) (8.8) (10.7) (8.7) (9.4)

Taking hypertension medication (%)c Black women White women Black menb White mena Totala

2.3 1.0 3.6 1.8 1.8

1.3 0.5 2.2 3.6 1.9

0.4 0.8 0.6 0.0 0.4

0.9 0.3 1.3 0.3 0.6

1.1 0.7 0.4 0.5 0.7

Elevated blood pressured (%) Black women White women Black mena White men Totala

6.9 3.8 16.4 10.6 8.1

5.7 1.9 18.5 10.6 9.1

3.6 1.2 13.7 7.9 6.1

6.7 2.0 12.9 6.6 6.5

3.6 1.8 6.5 6.5 4.3

Family history of hypertension (%) Black womenb White womenb Black men White men Totalb

60.1 50.1 54.8 44.6 50.9

63.9 46.1 56.0 43.8 53.4

54.7 39.8 59.0 42.5 48.5

51.5 45.8 47.8 45.3 47.3

58.8 38.9 52.6 40.2 48.9

p < 0.005 for differences among centers within race-sex groups. p < 0.05 for differences among centers within race-sex groups. c Some expected cell counts are less than five. d Elevated blood pressure is systolic pressure > 130 mmHg, diastolic pressure > 85 mmHg, or participant is taking anti-hypertensive medication. a

b

with the Midwest and West. A greater prevalence of severe overweight among white women and men for the two southern sites was also observed in the present study; whether corresponding associations with the incidence of diabetes will develop is yet to be determined. In the NHIS, the percentage of persons 18–44 years old who were told at least twice that they had high blood pressure was not different among men, but among women was greatest in the South, followed by the Midwest (17). In another CARDIA report (28), no differences among the four sites in elevated blood pressure were observed at the baseline exam. However, prevalence of elevated blood pressure was significantly greater among Birmingham men compared with the other sites seven years later (28), and the seven-year incidence was clearly highest in Birmingham, even after adjustment for pertinent covariates. The present report, which includes an additional southern site, lends support to the concept that geographic differences in ele-

vated blood pressure among young adults are likely, which is consistent with the observed higher stroke mortality in the South. Among men aged 18–44 years in the NHIS, smoking rates were lowest in the West and equally high in the South and Midwest; among women, smoking rates were highest in the Midwest and lowest in the West (17). In Bogalusa and Birmingham, smoking prevalence was greater among white women compared with black women, with no observed differences between black and white men. In the other sites, smoking prevalence was greater among blacks than whites for both women and men. The inverse association between educational level and smoking prevalence is well known (36), and is also well characterized in CARDIA (37). In this analysis, differences between the two educational levels ranged from 11.7% among black women in Birmingham to 55% among white women in Chicago; only 18.5% of white women with more

AEP Vol. 8, No. 1 January 1998: 22–30

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Greenlund et al. COMMUNITY DIFFERENCES IN CVD RISK FACTORS

TABLE 5. Adjusteda mean (standard error) body mass index and blood pressure, participants aged 20–31 years, CARDIA (1987–88) and the Bogalusa Heart study (1988–1991) Bogalusa

Birmingham

Chicago

Minneapolis

Oakland

2

Body mass index (kg/m ); mean (SE) Black women White women Black men White menb

27.0 24.1 25.7 25.8

(0.4) (0.2) (0.3) (0.2)

26.6 23.5 25.3 25.3

(0.4) (0.4) (0.3) (0.3)

26.7 23.5 24.7 24.7

(0.4) (0.3) (0.4) (0.3)

25.5 24.4 25.3 24.4

(0.5) (0.3) (0.3) (0.2)

26.5 23.7 25.0 24.1

(0.4) (0.3) (0.3) (0.3)

Systolic blood pressure (mmHg); mean (SE) Black womenb White womenb Black menb White menb

110.3 107.1 116.4 114.1

(0.5) (0.3) (0.7) (0.4)

106.2 101.9 115.3 112.0

(0.6) (0.6) (0.7) (0.6)

106.0 101.6 115.3 111.7

(0.6) (0.6) (0.8) (0.7)

106.5 104.1 115.4 112.9

(0.6) (0.5) (0.7) (0.5)

103.7 98.7 110.2 110.6

(0.5) (0.6) (0.7) (0.7)

Diastolic blood pressure (mmHg); mean (SE) Black womenb White womenc Black menb White menb

63.6 63.5 66.9 66.7

(0.5) (0.3) (0.7) (0.4)

67.2 64.9 72.9 70.9

(0.6) (0.6) (0.7) (0.6)

66.1 63.3 68.5 68.4

(0.6) (0.6) (0.8) (0.6)

66.6 64.0 68.8 68.0

(0.6) (0.5) (0.7) (0.5)

63.8 62.6 68.8 68.5

(0.5) (0.6) (0.7) (0.7)

a

Adjusted for age, smoking status, education, and alcohol consumption. Blood pressure also adjusted for body mass index. p < 0.005 for differences among centers within race-sex groups. c p < 0.05 for differences among centers within race-sex groups. b

than a high school education smoked, compared to 73.5% of those without. An increase in smoking prevalence of 15–35% with low educational attainment was observed in most race/gender/region subgroups. Regional differences may be related to significant local influences of both social pressures toward smoking and tobacco company marketing (38, 39). Some reported differences between the Bogalusa and CARDIA sites may be due to methodological differences. For example, mean blood pressure levels were higher in Bogalusa compared with the other sites, especially among women. Whether these differences may be due to the use of different types of blood pressure instruments is not known (40). Also, it is not known whether the differential followup rates for Bogalusa (15 years) and CARDIA (2 years) may be related to differences in observed risk factors through participation biases (i.e., who remains in long-term studies). On the other hand, the similarities between the levels for the Bogalusa and Birmingham sites, while being different from the other CARDIA sites, enhance the likelihood that the explanation may be geographic differences in risk factors and lifestyles. Further, the presence of more frequent antihypertensive drug therapy in the cohorts with higher mean systolic blood pressure also supports the validity of the observed differences. When comparing these results with other Bogalusa Heart study reports, it should be noted that use of the average of the second and third readings, as done here, resulted in slightly higher values than when the average of the six available readings are used, as has typically been reported for this study. The present study has shown the utility and feasibility of combining epidemiologic studies with similar, though not

identical, protocols to assess community differences in CVD risk factors. To some extent, these data suggest that geographic differences in risk factors may help explain regional differences in observed mortality for diseases such as stroke. More important, however, is the possibility for continued follow-up of these relatively young populations to more accurately assess the relationship between morbidity and mortality from a broader cross-section of diseases such as diabetes, atherosclerosis, stroke, chronic lung disease, lung cancer, and cirrhosis, with previously demonstrated risk as has been done in the Framingham (41) and Western Electric studies (42). The broader geographic base of these studies will allow the demonstration of important environmental causes of disease, as well as the establishment of regional priorities for public health intervention based on demonstrated associations between the prevalence of specific risk factors and later morbidity. CARDIA is supported by contracts NO1-HC-48047, NO1-HC-48048, NO1-HC-48049, and NO1-HC-48050 from the National Heart, Lung, and Blood Institute, National Institutes of Health. The Bogalusa Heart Study is supported by funds from the National Heart, Lung, and Blood Institute, National Institutes of Health, Grant H.L. 38844.

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