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.     

Trends in incidence, lifetime risk, severity, and 30-day mortality of stroke over the past 50 years

Context  Prior estimates of long-term trends in the incidence and severity of stroke have varied; trends in lifetime risk have not been reported. Objective  To determine long-term trends in the incidence, lifetime risk, severity, and 30-day mortality of clinical stroke. Design, Setting, and Participants  Prospective evaluation of the community-based Framingham Study original and offspring cohorts. Participants were 9152 men and women free of prevalent stroke and undergoing follow-up for up to 50 years over 3 consecutive periods (1950-1977, 1978-1989, and 1990-2004), with biennial ascertainment of stroke risk factor data and active surveillance for incident clinical stroke and cause-specific mortality. Main Outcome Measures  Incidence (age-adjusted, sex-specific), severity, 30-day mortality, and mortality-adjusted 10-year and lifetime risk of stroke in each of the specified periods. Results  There were 1030 incident clinical strokes (450 [44%] in men, 629 atherothrombotic brain infarctions [61%]) in 9152 persons 55 years or older over 174 917 person-years of follow-up. The age-adjusted incidence of first stroke per 1000 person-years in each of the 3 periods was 7.6, 6.2, and 5.3, respectively, in men (P = .02 for trend) and 6.2, 5.8, and 5.1 in women (P = .01 for trend). The lifetime risk at age 65 years decreased from 19.5% to 14.5% in men (P = .11) and from 18.0% to 16.1% in women (P = .61). Age-adjusted stroke severity did not vary across periods; however, 30-day mortality decreased significantly in men (from 23% to 14%; P = .01) but not significantly in women (from 21% to 20%; P = .32). Conclusions  In this cohort of men and women free of prevalent clinical stroke at initial examination, incidence of stroke has decreased over the past 50 years but the lifetime risk has not declined to the same degree, perhaps due to improved life expectancy. The results of this study suggest that improved control of risk factors has lowered stroke incidence but emphasize the need for continued primary prevention efforts.      

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.     

Search for an optimal atherogenic lipid risk profile: from the Framingham Study

Recent guidelines have targeted low-density lipoprotein (LDL) cholesterol for treatment of dyslipidemia. A lack of clear demarcation of potential coronary heart disease (CHD) cases solely on the basis of LDL cholesterol indicates the need to consider the dyslipidemic risk in the context of a lipid and risk factor profile. We prospectively examined the influence of individual lipids and their ratios on 20-year CHD development in 2,439 men and 2,812 women participating in the Framingham Offspring Study. The influence of the total/high-density (HDL) cholesterol ratio on CHD risk was examined in tertiles of LDL cholesterol and total cholesterol levels. During the 20-year period, 566 CHD events occurred in men and 327 events in women. The CHD risk increased stepwise two- to threefold in men and women from the first to third tertile of total/HDL cholesterol ratio, irrespective of the level of total or LDL cholesterol level. In men, the LDL cholesterol level reflected the lowest risk factor adjusted quintile 5 to quintile 1 relative risk (1.85), and the total/HDL cholesterol ratio predicted the greatest risk (relative risk 2.9). In women, LDL cholesterol imparted the highest risk of the individual lipids (relative risk 3.9), and this was not exceeded by the lipid ratio (relative risk 3.8). In conclusion, the levels of components of the total/HDL cholesterol ratio have little influence on its prediction of CHD. In men, elevated LDL need not be treated aggressively if the total/HDL cholesterol ratio is low. Conversely, modest elevations of LDL may warrant more aggressive treatment if the ratio is high. In women, the ratio is also a good CHD predictor, but a combination of a high ratio accompanied by high LDL cholesterol may warrant more aggressive therapy.     

Metabolic syndrome compared with type 2 diabetes mellitus as a risk factor for stroke: the Framingham Offspring Study

BACKGROUND: Metabolic syndrome (MetS) has been recognized as a prediabetic constellation of symptoms and an independent risk factor for cardiovascular disease. METHODS: To evaluate the age-adjusted risk of stroke and population-attributable risk associated with MetS and compare with those of overt type 2 diabetes mellitus (hereinafter, "diabetes"), we determined the prevalence of MetS alone, diabetes alone, and both in 2097 subjects in the Framingham Offspring Study, aged 50 to 81 years and free of stroke. Age-adjusted risk ratios, 10-year incidence, and population-attributable risks of stroke were estimated for men and women with MetS alone, diabetes alone, and both. RESULTS: Criteria for MetS were met in 30.3% of men and 24.7% of women. Twenty-four percent of men had MetS alone; 7% had diabetes alone; and 6% had both. Twenty percent of women had MetS alone; 3% had diabetes alone; and 5% had both. Over 14 years of follow-up, 75 men and 55 women developed a first stroke; all but 4 events were ischemic. Relative risk (RR) of stroke in persons with both diabetes and MetS (RR, 3.28; confidence interval [CI], 1.82-5.92) was higher than that for either condition alone (MetS alone: RR, 2.10; CI, 1.37-3.22; diabetes alone: RR, 2.47; CI, 1.31-4.65). The population-attributable risk, owing to its greater prevalence, was greater for MetS alone than for diabetes alone (19% vs 7%), particularly in women (27% vs 5%). CONCLUSIONS: Metabolic syndrome is more prevalent than diabetes and a significant independent risk factor for stroke in people without diabetes. Prevention and control of MetS and its components are likely to reduce stroke incidence.