FRAMINGHAM STUDY

The Framingham Heart Study is a longitudinal study of a defined population in Massachusetts, initiated in 1948. The Framingham Study was conceived by Joseph Mountin, Assistant Surgeon General and head of the Division of Chronic Diseases of the U.S. Public Health Service. Mountin saw that cardiovascular diseases were replacing infectious diseases as the major cause of mortality in the United States. He responded to the suggestion of David Rutstein of Harvard University that the study be set up in Framingham, Massachusetts, a Boston suburb. The study was soon incorporated into the newly established National Heart Institute (NHI), part of the National Institutes of Health (NIH), by NHI director C. J. Van Slyke. Felix Moore, the chief of biometrics at NHI, was charged with estimating the required sample size for a definitive epidemiological study that had a reasonable likelihood of establishing, during a twenty-year period, the relationship between given characteristics and the risk of death from heart attack. This resulted in a study sample of 5,209 Framingham men and women between the ages of thirty and sixty.

Early opposition to epidemiological studies at NIH was overcome, in part due to the arguments of Van Slyke's chief cardiological advisor, Boston cardiologist Paul Dudley White, who had become interested in the natural history of heart diseases as a student in England. Dr. Thomas Dawber was appointed director of the study, and he brought his own ideas to what was to become the best-known cohort study of all time. In his book, The Framingham Study (1980), Dawber wrote:

The task of epidemiology … is to determine to what degree an observed relationship may be the result of chance and at what point the relationship is sufficiently strong that it may well be involved in causality (p. 5).

The characteristics of persons who already have the disease are not necessarily the same as those that predispose to the disease. Observations of population characteristics must be made well before disease becomes overt if the relationship of these characteristics to the development of the disease is to be established with reasonable certainty (p.11).

If the relationship is one that fits what is known about the disease and has a logical explanation, it is worth exploring further, regardless of the strength of the relationship. If, however, the relationship is very powerful, it deserves careful scrutiny even though the alleged relationship may be unexplained at the time (p. 4).

The ongoing Framingham Study has remained the responsibility of the NHI, which was renamed the National Heart, Lung, and Blood Institute (NHLBI) in 1976, and it is carried out under contract by researchers at the Boston University School of Medicine. It has been enlarged twice, in 1971 with the "Offspring Study," which added 5,124 children (and their spouses), to the original study participants, and in the late 1990s with the "Omni Study" of minorities. Every other year, after an extensive baseline examination, subjects undergo testing that includes a medical history, blood profile, echocardiogram, and bone, eye, and other specialized tests.

The Framingham Study produced a landmark report on the predictive power of blood pressure, blood cholesterol level, and cigarette smoking for heart and blood vessel diseases (Dowbar et al.,1957). The term "risk factor" is, in fact, attributed to the investigators of Framingham, who have also gone on to elaborate many central concepts and practical tools in the identification and prevention of elevated cardiovascular risk. Among their discoveries are:

• Knowledge about the relationship between blood vessel diseases and blood cholesterol fractions, LDL ("bad") cholesterol and HDL ("good") cholesterol.
• "Multivariate risk"—the more-than-additive contribution to risk of multiple factors present together.
• The greater predictive precision of systolic, rather than diastolic, blood pressure levels.
• Discounting the "common wisdom" that high blood pressure is less dangerous in women and the elderly.
• The rising risk of cardiovascular diseases among women after menopause.
• The halving of heart attack risk within a few years after stopping smoking.

The Framingham Study, with congruent findings from other studies in the United States and abroad, sparked a revolution in understanding the individual and the mass causes, as well as the preventability, of heart attack and stroke. It provided a sound basis for successful medical action and health-promotion policies to reduce the death rate from these diseases.

Under the leadership of William Kannel, in recent years the Framingham researchers have also studied the risk of particular disease manifestations such as heart failure, peripheral artery disease, stroke types, and arrhythmias. New risk characteristics such as the apolipoproteins and their regulating genes, homocysteine, blood clotting factors, and inflammation have also been examined. The scope of the study has widened to include chronic conditions such as obesity, diabetes, cardiac enlargement, osteoporosis, cancer, and Alzheimer's disease.

Henry Blackburn

(see also: Behavior, Health-Related; Cardiovascular Diseases; Chronic Illness; Cohort Study; Coronary Artery Disease; Epidemiologic Transition; Multifactorial Diseases; National Institutes of Health; Noncommunicable Disease Control; Observational Studies; Risk Assessment, Risk Management )

Bibliography

Dawber, T. R. (1980). The Framingham Study. The Epidemiology of Atherosclerotic Disease. Cambridge, MA: Harvard University Press.

Dawber, T. R.; Moore, F. E., Jr.; and Mann, G. V. (1957). "Coronary Heart Disease in the Framingham Study." American Journal of Public Health 47:4–24.

Kannel, W. B. (1995). "Clinical Misconceptions Dispelled by Epidemiological Research. The Ancel Keys Lecture." Circulation 92:3350–3360.