The relationship of obesity and the development of coronary heart disease to longitudinal changes in systolic blood pressure.
In an investigation of the relationship of obesity and the development of coronary heart disease (CHD) to longitudinal changes in systolic blood pressure (SBP), a sample of 1029 male participants from the Baltimore Longitudinal Study of Baltimore (BLSA), who were free of CHD at the beginning of the study, were examined with a total of 4111 examinations (mean of four examinations per person) conducted during the study period. The mean follow-up time was 8.1 years with a maximum of 16 examinations and 30.9 years of follow-up. During the follow-up period, 192 participants developed CHD, and these participants' data collected after the CHD event were excluded from the analysis. A proportional hazards regression model was used to calculate the relative risk of developing CHD for several CHD risk factors. Both simple and multiple proportional hazards regression models indicate a strong association between body mass index (BMI), cholesterol, cigarette smoking, and systolic blood pressure (SBP) with the risk of developing CHD. In addition, a linear mixed-effects model was used to examine changes in SBP measurements over time and to identify factors, including the age at first examination and time in study, that are related to that change. The results from the linear mixed-effects model analysis indicate that those in the obese group (BMI > or = 30 kg/m2) have SBP measurements that are on average 9.0 mm Hg higher than those in the normal group (20 < or = BMI < 25). Also, SPB measurements were on average 6.6 mm Hg higher in those who developed CHD during the study period than those who remained free of disease. In addition, SPB showed a quadratic relationship with time, and its patterns of change with time were different among the different age groups. Also, the relationship between changes in SBP with respect to cholesterol was dependent on time in the study as well.