Bogalusa Heart Study

Background/Questions

The Bogalusa Heart Study is seated in a small Louisiana town. It began in 1972 as a pioneering study of biologic and behavioral CVD risk factors in youth, their distribution and evolution with age (tracking), and their trends over time. The object was to improve understanding of the pathogenesis of adult disease.

Method/Design

The initial cross-sectional survey during the school year of 1973-1974 included 3.524 children, ages 5 ˆ14, 93% of the eligible population residing in Ward 4 (Bogalusa) of Washington Parish, Louisiana, 63% white and the remainder black. An additional 714 children between the ages of two and one half to five and one half years were examined during the summer of 1974.

Five cross-sectional surveys were completed between 1976 and 1985, with responses ranging from 79% to 92%. Follow-up into early adulthood was initiated in 1978 among the cohort of children born between 1959 and 1969. Standardized protocols were scheduled throughout the year to take into account seasonal influences on risk factors. Special efforts were made to minimize problems with data collection due to the relatively young age of the cohort, with tests of reproducibility and selected interviews with the mothers. Information on the presence of CVD risk factors in the children’s parents was collected for some subgroups.

Later examinations in a subset of the cohort included CT scans to detect coronary artery calcium or ultrasonography for the measurement of carotid artery intimal hyperplasia.

Results

Children in the upper percentiles for specific risk factors, such as blood pressure and body mass index, were more likely to have abnormal levels of these risk factors as adults; risk factors for CVD tended to cluster. For example, subjects in the upper quartile of blood pressure tended to be in the upper quartiles for cholesterol and weight.

White children had significantly lower serum cholesterol values than blacks (162 mg/dl vs. 170 mg/dl). Serum cholesterol levels were correlated with serum triglyceride levels to a greater extent in white than in black children for boys and girls.

Protein, carbohydrate and fat consumption comprised 13%, 49%, and 38% of the children’s total caloric intake respectively at the entry survey. White girls consumed fewer calories and less protein, fat, cholesterol, carbohydrate and sodium than the other race/sex groups. White boys had the highest consumption of fat and total calories, while black girls had the highest intake of sodium.

A follow-up dietary survey of 6 cohorts of 10-year-olds showed that total energy intake remained virtually the same between 1973 and 1988, ranging from 2,000 to 2,200 kilocalories. There were no racial differences in total caloric intake but boys had consistently higher energy intakes than girls. The proportion of energy from fat declined over time from 38% in 1973-74 to 36% in the most recent survey year of 1987-88. Intake of dietary cholesterol declined over time (324 mg in 1973; 285 mg in 1987) while the consumption of sodium increased progressively from 3.3 grams in 1973 to 3.8 grams in 1988. Dietary data suggested that most children in Bogalusa exceeded national recommendations for the intake of total and saturated fat.

Black children had higher levels of serum cholesterol compared to white children; and lower levels of serum triglycerides. Increases in serum triglycerides during puberty were seen in all groups with the exception of black girls. A decline in HDL-cholesterol levels was seen in all four groups but was most pronounced in white boys who tended to have the highest prevalence of an unfavorable lipid profile. Associations were seen between obesity, serum cholesterol level and blood pressure in all groups. Young black women had a higher prevalence of obesity than black men or white men and women. Overall, HDL-cholesterol levels were higher in black females. Total cholesterol distributions were similar for all four race/sex groups.

In black men a positive association was seen between baseline levels of systolic and diastolic blood pressure and serum creatinine levels over time. Thus. young black men may be at increased risk for impaired renal function and elevated blood pressure.

More extensive aortic surface involvement with fatty streaks was seen among the autopsied black men and women compared with whites even after controlling for CVD risk factors. The presence and extent of both fatty streaks and fibrous plaques in the aorta and coronary arteries increased with age. Levels of BMI, blood pressure, and serum cholesterol and triglycerides were highly correlated with the extent of pathologic lesions found in the aorta and coronary arteries.

A health habits survey administered during one school year to approximately 2900 children between the ages of 8 and 17 years showed that more than half of respondents reported having tried cigarette smoking. Boys in each age cohort tried cigarettes at an earlier age than girls as did white compared to black children. There were trends towards trying smoking cigarettes at increasingly earlier ages for each age cohort under study. For smokers, the smoking habit appeared to have become established by the age of 14 years.

Steady increases in stature throughout childhood were noted. Few differences in body weight were noted between black and white boys until adulthood when young white men were on average, approximately 10 pounds heavier than young black men. Black girls tended to be approximately 2 to 4 kilograms heavier than white girls throughout most of childhood. Young adult black women, however, were significantly heavier than young white women. Relatively similar trends in BMI and skinfold thickness measures were observed.

Increases in weight over all ages were observed over the 15 year period under study (1973-1988) with particularly marked changes among children in the uppermost quartiles suggesting a shift to the right in the distribution of weight. Central obesity was associated with abnormal glucose metabolism, an adverse serum lipid profile, and elevations in blood pressure, most pronounced after puberty and into early adulthood. Abnormal glucose metabolism in children was associated with a parental history of adult onset diabetes.

Conclusions/Discussion

This is one of few longitudinal studies of children followed into young adult years and continues to date. It called early attention to the pediatric roots of coronary atherosclerosis in a biracial community. It is a classic of youth studies, pioneered in many methods, and was the first (not reviewed here) to test and recommend medications for the control of blood pressure and lipids in the upper fractile of the distribution among children. Considerable loss to follow up occurred as the cohort aged and became more mobile.