The NHLBI twin study of cardiovascular disease risk factors: methodology and summary of results

Coronary heart disease (CHD) risk factors were studied in 250 monozygotic (MZ) and 264 dizygotic (DZ) male veteran twin pairs, aged 42-56. All coronary heart disease risk factors studied showed significant correlations in both MZ and DZ twins. Substantial genetic variation was detected for height, blood pressure, glucose intolerance, uric acid, plasma triglyceride, and relative weight but little or no significant genetic variability in low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL), total plasma cholesterol or hematocrit was demonstrable. These findings suggest that familial aggregation results from genetic influence on blood pressure, glucose intolerance, uric acid, triglyceride and, possibly, obesity, while largely shared environmental factors contribute to familial similarities in HDL, LDL, total cholesterol and hematocrit.     

Epidemiologic assessment of chronic atrial fibrillation and risk of stroke: the Framingham study

Chronic atrial fibrillation (AF) as a precursor of stroke was assessed over 24 years of follow-up of the general population sample at Framingham, Massachusetts. Persons with chronic established AF, with or without rheumatic heart disease (RHD), are at greatly increased risk of stroke, and the stroke is probably due to embolism. Chronic AF in the absence of RHD is associated with more than a fivefold increase in stroke indicence, while AF with RHD has a 17-fold increase. Stroke occurrence increased as duration of AF increased, with no evidence of a particularly vulnerable period. Chronic idiopathic AF is an important precursor of cerebral embolism. Controlled trials of anticoagulants or antiarrhythmic agents in persons with chronic AF may demonstrate if strokes can be prevented in this highly susceptible group.     

Cholesterol in the prediction of atherosclerotic disease. New perspectives based on the Framingham study.

Prospective data at Framingham and elsewhere have shown conclusively that risk of coronary heart disease in persons younger than age 50 is strikingly related to the serum total cholesterol level. Within so-called normal limits risk has been found to mount over a five-fold range. The impact has been found to be augmented by other risk factors. The contribution of the serum total cholesterol to risk has also been found to be determined by its partition in the various lipoprotein fractions. A relatively large amount of cholesterol in the low-density lipoprotein fraction is atherogenic, whereas that in the high-density fraction appears protective. The independent contribution of very-low density lipoprotein and its triglyceride or cholesterol content has, on the other hand, not been established. The previous position that virtually all of the lipid information pertaining to coronary heart disease resided in the serum total cholesterol must be accordingly modified.     

Proportional hazards analysis of risk factors for coronary heart disease in individuals aged 65 or older. The Framingham Heart Study

Risk factors for coronary heart disease were examined in 2,501 individuals in the Framingham Heart Study who survived to the age of 65 without evidence of coronary artery disease. We used a proportional hazards (Cox) analysis that examined risk factors over time and included events through the 16th biennial examination. The independently significant multivariate correlates of the development of coronary heart disease after the age of 65 were sex (incidence rate ratio [RR] for males of 1.7 [95% confidence interval of 1.4,2.0]), left ventricular hypertrophy (RR = 2.4 [1.7,3.5]), systolic blood pressure (RR = 2.2 [1.4,3.3] for systolic blood pressure of 160 mmHg or higher as compared with less than 120 mmHg), casual blood glucose (RR = 2.2 [1.5,3.4] for 175 mg/dL or more as compared with less than 90 mg/dL), Metropolitan relative weight from examination 1 (RR = 1.3 [1.0,1.6] for those 130% or more of ideal weight compared with those less than 110% of ideal), and total serum cholesterol (RR = 1.8 [1.3,2.5] for cholesterol in the 90th percentile or higher compared with less than 200 mg/dL). Controlling for all these risk factors, those smoking 20 cigarettes a day or more were at slightly increased risk of coronary heart disease (RR = 1.2 [.9,1.6]) compared with nonsmokers. These analyses suggest that older persons share the same risk factors for coronary artery disease that are significant in younger populations.