Framingham Heart Study


The Framingham Heart Study is a long-term, ongoing cardiovascular cohort study of residents of the city of Framingham, Massachusetts. The study began in 1948 with 5,209 adult subjects from Framingham, and is now on its fourth generation of participants. Prior to the study almost nothing was known about the epidemiology of hypertensive or arteriosclerotic cardiovascular disease. Much of the now-common knowledge concerning heart disease, such as the effects of diet, exercise, and common medications such as aspirin, is based on this longitudinal study. It is a project of the National Heart, Lung, and Blood Institute, in collaboration with Boston University. Various health professionals from the hospitals and universities of Greater Boston staff the project.

History

In 1948, the study was commissioned by Congress, with a choice made between Framingham, Massachusetts and Paintsville, Kentucky. Framingham was chosen when residents showed more general interest in heart research than Paintsville. Thomas Royle Dawber was Director of the study from 1949 to 1966. He was appointed as chief epidemiologist shortly after the start of the project, when it was not progressing well.
The study had been intended to last 20 years; however, interest grew in part due to Dr. Dawber's efforts to promote the study and engage in fundraising after he had been transferred to Boston to accept a chairmanship of preventive medicine.
By 1968, it was debated whether the original study had served its purpose and should be terminated as scheduled. A committee gathered and considered that, after 20 years of research, the Framingham study should come to an end, since their hypothesis had been tested and extensive information concerning heart diseases had been gathered. Despite this conclusion, Congress failed to accept the recommendation, instead voting to continue the study.
The study has been split into different segments, or "cohorts".
Over 3,000 peer-reviewed scientific papers have been published related to the Framingham Heart Study. It is generally accepted that the work is outstanding in its scope and duration, and overall is considered very useful.
It was rightly assumed from the start of the Framingham Heart Study that cardiac health can be influenced by lifestyle and environmental factors, and by inheritance. The Framingham Heart Study is the source of the term risk factor. Before the Framingham Heart Study, doctors had little sense of heart disease prevention. In the 1950s, it was believed that clogging of arteries and narrowing of arteries were normal parts of aging, and that they occurred universally as people became older. High blood pressure and elevated serum cholesterol were also seen as normal consequences of aging in the 1950s, and no treatment was available. These and further risk factors, such as homocysteine, were gradually discovered over the years.
The Framingham Heart Study, along with other important large studies, such as the Seven Countries Study and the Nurses' Health Study, also showed that healthy diet, not being overweight or obese, and regular exercise are all important in maintaining good health, and that there are differences in cardiovascular risk between men and women. Along with other important studies about smoking, such as the British Doctors Study, it also confirmed that cigarette smoking is a highly significant factor in the development of heart disease, leading in many cases to angina pectoris, myocardial infarction, and coronary death.
Recently the Framingham studies have come to be regarded as overestimating risk, particularly in the lower risk groups, such as for UK populations.
One question in evidence-based medicine is how closely the people in a study resemble the patient with whom the health care professional is dealing.
Researchers recently used contact information given by subjects over the last 30 years to map the social network of friends and family in the study.

Framingham Risk Score

The 10-year cardiovascular risk of an individual can be estimated with the Framingham Risk Score, including for individuals without known cardiovascular disease. The Framingham Risk Score is based on findings of the Framingham Heart Study.

Major findings

Major findings from the Framingham Heart Study, according to the researchers themselves:
;1960s: Cigarette smoking increases risk of heart disease. Increased cholesterol and elevated blood pressure increase risk of heart disease. Exercise decreases risk of heart disease, and obesity increases it.
;1970s: Elevated blood pressure increases risk of stroke. In women who are postmenopausal, risk of heart disease is increased, compared with women who are premenopausal. Psychosocial factors affect risk of heart disease.
;1980s: High levels of HDL cholesterol reduce risk of heart disease. No empirical evidence found to confirm the rumor that filtered cigarettes lower risk of heart disease as opposed to non-filters.
;1990s: Having an enlarged left ventricle of the heart increases risk of stroke. Elevated blood pressure can progress to heart failure. Framingham Risk Score is published, and correctly predicts 10-year risk of future coronary heart disease events. At 40 years of age, the lifetime risk for CHD is 50% for men and 33% for women.
;2000s:So called "high normal blood pressure" increases risk of cardiovascular disease. Lifetime risk of developing elevated blood pressure is 90%. Obesity is a risk factor for heart failure. Serum aldosterone levels predict risk of elevated blood pressure. Lifetime risk for obesity is approximately 50%. The "SHARe" project is announced, a genome wide association study within the Framingham Heart Study. Social contacts of individuals are relevant to whether a person is obese, and whether cigarette smokers decide to quit smoking. By providing contact information, the Framingham Heart Study establishes a network of personal relationships, connecting participants through their relationships—friends, colleagues, relatives and neighbors. Four risk factors for a precursor of heart failure are discovered. 30-year risk for serious cardiac events can be calculated. American Heart Association considers certain genomic findings of the Framingham Heart Study one of the top research achievements in cardiology. Some genes increase risk of atrial fibrillation. Risk of poor memory is increased in middle aged men and women if the parents had suffered from dementia.

Study design

The Framingham Heart Study participants, and their children and grandchildren, voluntarily consented to undergo a detailed medical history, physical examination, and medical tests every three to five years, creating a wealth of data about physical and mental health, especially about cardiovascular disease. A nonprofit charity, called Friends of the Framingham Heart Study, was founded to help defray study costs and spread awareness of heart issues. Membership is limited to participants.

Genetic research

In recent years, scientists have been carrying out genetic research within the Framingham Heart Study.
Inheritance patterns in families, heritability and genetic correlations, molecular markers, and associations have been studied. The association studies include traditional genetic association studies, i.e., looking for associations of cardiovascular risk with gene polymorphisms in candidate genes, and genome wide association studies. For example, one genome wide study, called the 100 K Study, included almost 1400 participants of the Framingham Heart Study, and revealed a genetic variant associated with obesity. The researchers were able to replicate this particular result in four other populations. Further, the SHARe Study uncovered new candidate genes, and confirmed already known candidate genes in participants of the Framingham Heart Study.
Because of these exciting genomic results, the Framingham Heart Study has been described as "on its way to becoming the gold standard for cardiovascular genetic epidemiology".
However, clinically, despite these efforts, the aggregate effect of genes on cardiovascular disease risk beyond that of traditional cardiovascular risk factors has not been established.

Similar studies

Works cited