In 1948, the study was commissioned by the United States Congress, with multiple communities being considered for study. The final choice was 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.[3] 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".[citation needed]
The Original Cohort, founded in 1948, consisted of 5,209 men and women. Requirements for entry were an age between 30 and 62 years at the time of first examination, with no history of heart attack or stroke. Due to lukewarm interest at first, doctors, nurses and healthcare workers volunteered for the study to set an example for patients.
The Offspring Cohort, founded in 1971, was a second-generation study for which children of the Original Cohort were eligible. Spouses were also eligible if they had become pregnant with or sired two or more children by a participant in the Offspring Cohort.
The Omni One Cohort, founded in 1994, looked at the possible influence of race and heritage as heart risk factors, as well as the changing racial background of Framingham.
The Generation Three Cohort, founded in 2002, was a third-generation study consisting of children of the Offspring Cohort and grandchildren of the Original Cohort participants. Minimum age for acceptance was 20 years.
The Omni Two Cohort, founded in 2003, was a second-generation study involving children of Omni Cohort participants. While the Original Cohort had been spaced over decades, the Omni Cohort had a much shorter generational window. On account of this, participants as young as 13 years of age were eligible for the Omni Two Cohort.
Strengths & weaknesses
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.[citation needed]
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 (atherosclerosis, arteriosclerosis) were normal parts of aging, and that they occurred universally as people became older. High blood pressure (hypertension) and elevated serum cholesterol (hypercholesterolemia) 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.[5][6][7][8][9]
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.[10][11] 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 (MI), and coronary death.[12][13]
Recently the Framingham studies have come to be regarded as overestimating risk, particularly in the lower risk groups, such as for UK populations.[14]
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.[15]
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.[16]
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.[citation needed]
Major findings
Major findings from the Framingham Heart Study, according to the researchers themselves:[17]
1960s
Cigarette smoking is associated with increased risk of heart disease. Increased cholesterol and elevated blood pressure is associated with increased risk of heart disease. Exercise is associated with decreased risk of heart disease, and obesity with increased risk.
1970s
Elevated blood pressure is associated with increased 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 is associated with lower risk of heart disease. No empirical evidence found to confirm the rumor that filtered cigarettes lower the risk of heart disease as opposed to non-filters. Elevated levels of fibrinogen are associated with an increased risk of coronary artery disease and stroke.[18][19]
1990s
Having an enlarged left ventricle of the heart (left ventricular hypertrophy) is associated with increased 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 (CHD) 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" is associated with increased risk of cardiovascular disease (high normal blood pressure is called prehypertension in medicine; it is defined as a systolic pressure of 120–139mm Hg and/or a diastolic pressure of 80–89mm Hg). 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.[20] 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 had 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,[21] 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.[citation needed]
Genetic research
In recent years, scientists have been carrying out genetic research within the Framingham Heart Study.
Inheritance patterns in families,[22] heritability and genetic correlations,[23] molecular markers,[24] and associations have been studied. The association studies include traditional genetic association studies, i.e., looking for associations of cardiovascular risk with gene polymorphisms (single-nucleotide polymorphisms, SNPs) in candidate genes, and genome wide association studies (GWAS).[9] For example, one genome wide study, called the 100 K Study, included almost 1400 participants of the Framingham Heart Study (from the original cohort, and the offspring cohort), and revealed a genetic variant associated with obesity. The researchers were able to replicate this particular result in four other populations.[25] Further, the SHARe Study (SNP Health Association Resource Study) uncovered new candidate genes, and confirmed already known candidate genes (for homocysteine and vitamin B12 levels) in participants of the Framingham Heart Study.[26]
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".[27]
However, clinically, despite these (and other) efforts, the aggregate effect of genes on cardiovascular disease risk beyond that of traditional cardiovascular risk factors has not been established.[28]
Similar studies
The Busselton Health Study has been carried out since 1966 in a high proportion of the residents of Busselton, a town in Western Australia, over a period of many years.[29] A database has been compiled and is managed by the School of Population Health at the University of Western Australia. Although the results of the Busselton Health Study and the Framingham Heart Study are similar in many aspects, the Busselton Health Study also investigated the influence of some factors that had not been investigated in the Framingham Heart Study, e.g., sleep apnea.[30][31]
The Caerphilly Heart Disease Study, also known as the Caerphilly Prospective Study (CaPS), is an epidemiological prospective cohort, set up in 1979 in a representative population sample drawn from a typical small town in South Wales, UK.[32] The study has collected wide-ranging data and has led to over 400 publications in the medical press, notably on vascular disease, cognitive function and healthy living.[33][34]
The China–Cornell–Oxford Project, also known as the "China–Oxford–Cornell Study on dietary, lifestyle and disease mortality characteristics in 65 rural Chinese counties". This study was later referred to as "China Study I". The successor study is named "China Study II".[35]
The Copenhagen City Heart Study, also known as Østerbroundersøgelsen in Danish (referring to the Eastern part of Copenhagen "Østerbro"), is an ongoing prospective cohort study of cardiovascular disease and its risk factors among Danish men and women. The original cohort began in 1976 with 19,698 participants ages 20–93 ].[37] To date over 930 articles have been published and 76 PhD dissertations defended based on data from the study.[38] Notable findings from the study include the benefits of physical activity in old age, clinical implication of elevated triglyceride levels and effect of genetic disposition of development of cancer and cardiovascular disease. "Østerbroundersøgelsen - Den Store Danske (Danish)".
↑ Thomas R. Dawber, M.D., Gilcin F. Meadors, M.D., M.P.H., and Felix E. Moore Jr., National Heart Institute, National Institutes of Health, Public Health Service, Federal Security Agency, Washington, D. C., Epidemiological Approaches to Heart Disease: The Framingham Study Presented at a Joint Session of the Epidemiology, Health Officers, Medical Care, and Statistics Sections of the American Public Health Association, at the Seventy-eighth Annual Meeting in St. Louis, Mo., November 3, 1950.
1 2 Govindaraju DR, Cupples LA, Kannel WB, O'Donnell CJ, Atwood LD, D'Agostino RB Sr, Fox CS, Larson M, Levy D, Murabito J, Vasan RS, Splansky GL, Wolf PA, Benjamin EJ (2008). "Chapter 2 Genetics of the Framingham Heart Study Population". Advances in Genetics. Vol.62. pp.33–65. doi:10.1016/S0065-2660(08)00602-0. ISBN978-0-12-374443-2. PMC3014216. PMID19010253.
↑ Nutritional research within the Framingham Heart Study. Millen BE, Quatromoni PA. J Nutr Health Aging. 2001;5(3):139-43.
↑ Women and cardiovascular disease: contributions from the Framingham Heart Study. Murabito JM. J Am Med Womens Assoc. 1995 Mar-Apr;50(2):35-9.
↑ The health risks of smoking. The Framingham Study: 34 years of follow-up. Freund KM, Belanger AJ, D'Agostino RB, Kannel WB. Ann Epidemiol. 1993 Jul;3(4):417-24.
↑ Mortality in relation to smoking: 50 years' observations on male British doctors. Doll R, Peto R, Boreham J, Sutherland I. BMJ. 2004 Jun 26;328(7455):1519.
↑ Overview of the risk factors for cardiovascular disease. Wilson PWF. In: UpToDate [Textbook of Medicine]. Basow DS (Ed). Massachusetts Medical Society, and Wolters Kluwer publishers. 2010.
Daniel Levy and Susan Brink. (2005). A Change of Heart: How the People of Framingham, Massachusetts, Helped Unravel the Mysteries of Cardiovascular Disease. Knopf. ISBN0-375-41275-1.
Further reading
Giroux Élodie (2012). "The Framingham Study and the Constitution of a Restrictive Concept of Risk Factor". Social History of Medicine. 26 (1): 94–112. doi:10.1093/shm/hks051.
Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves the reduction of blood flow to the cardiac muscle due to build-up of atherosclerotic plaque in the arteries of the heart. It is the most common of the cardiovascular diseases. Types include stable angina, unstable angina, and myocardial infarction.
Hypertension, also known as high blood pressure, is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms itself. It is, however, a major risk factor for stroke, coronary artery disease, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia. Hypertension is a major cause of premature death worldwide.
A cohort study is a particular form of longitudinal study that samples a cohort, performing a cross-section at intervals through time. It is a type of panel study where the individuals in the panel share a common characteristic.
Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases, heart failure, hypertensive heart disease, rheumatic heart disease, cardiomyopathy, arrhythmia, congenital heart disease, valvular heart disease, carditis, aortic aneurysms, peripheral artery disease, thromboembolic disease, and venous thrombosis.
The British Doctors' Study was a prospective cohort study which ran from 1951 to 2001, and in 1956 provided convincing statistical evidence that tobacco smoking increases risk of lung cancer.
Essential hypertension is a form of hypertension without an identifiable physiologic cause. It is the most common type affecting 85% of those with high blood pressure. The remaining 15% is accounted for by various causes of secondary hypertension. Essential hypertension tends to be familial and is likely to be the consequence of an interaction between environmental and genetic factors. Hypertension can increase the risk of cerebral, cardiac, and renal events.
The Women's Health Initiative (WHI) was a series of clinical studies initiated by the U.S. National Institutes of Health (NIH) in 1991, to address major health issues causing morbidity and mortality in postmenopausal women. It consisted of three clinical trials (CT) and an observational study (OS). In particular, randomized controlled trials were designed and funded that addressed cardiovascular disease, cancer, and osteoporosis.
The Whitehall Studies investigated social determinants of health, specifically the cardiovascular disease prevalence and mortality rates among British civil servants. The initial prospective cohort study, the Whitehall I Study, examined over 17,500 male civil servants between the ages of 20 and 64, and was conducted over a period of ten years, beginning in 1967. A second cohort study, the Whitehall II Study, was conducted from 1985 to 1988 and examined the health of 10,308 civil servants aged 35 to 55, of whom two thirds were men and one third women. A long-term follow-up of study subjects from the first two phases is ongoing.
The Nurses' Health Study is a series of prospective studies that examine epidemiology and the long-term effects of nutrition, hormones, environment, and nurses' work-life on health and disease development. The studies have been among the largest investigations into risk factors for major chronic diseases ever conducted. The Nurses' Health Studies have led to many insights on health and well-being, including cancer prevention, cardiovascular disease, and type 2 diabetes. They have included clinicians, epidemiologists, and statisticians at the Channing Laboratory, Harvard Medical School, Harvard School of Public Health, and several Harvard-affiliated hospitals, including Brigham and Women's Hospital, Dana–Farber Cancer Institute, Children's Hospital Boston, and Beth Israel Deaconess Medical Center.
A non-communicable disease (NCD) is a disease that is not transmissible directly from one person to another. NCDs include Parkinson's disease, autoimmune diseases, strokes, heart diseases, cancers, diabetes, chronic kidney disease, osteoarthritis, osteoporosis, Alzheimer's disease, cataracts, and others. NCDs may be chronic or acute. Most are non-infectious, although there are some non-communicable infectious diseases, such as parasitic diseases in which the parasite's life cycle does not include direct host-to-host transmission.
A prospective cohort study is a longitudinal cohort study that follows over time a group of similar individuals (cohorts) who differ with respect to certain factors under study, to determine how these factors affect rates of a certain outcome. For example, one might follow a cohort of middle-aged truck drivers who vary in terms of smoking habits, to test the hypothesis that the 20-year incidence rate of lung cancer will be highest among heavy smokers, followed by moderate smokers, and then nonsmokers.
The obesity paradox is the finding in some studies of a lower mortality rate for overweight or obese people within certain subpopulations. The paradox has been observed in people with cardiovascular disease and cancer. Explanations for the paradox range from excess weight being protective to the statistical association being caused by methodological flaws such as confounding, detection bias, reverse causality, or selection bias.
Cognitive epidemiology is a field of research that examines the associations between intelligence test scores and health, more specifically morbidity and mortality. Typically, test scores are obtained at an early age, and compared to later morbidity and mortality. In addition to exploring and establishing these associations, cognitive epidemiology seeks to understand causal relationships between intelligence and health outcomes. Researchers in the field argue that intelligence measured at an early age is an important predictor of later health and mortality differences.
The Framingham Risk Score is a sex-specific algorithm used to estimate the 10-year cardiovascular risk of an individual. The Framingham Risk Score was first developed based on data obtained from the Framingham Heart Study, to estimate the 10-year risk of developing coronary heart disease. In order to assess the 10-year cardiovascular disease risk, cerebrovascular events, peripheral artery disease and heart failure were subsequently added as disease outcomes for the 2008 Framingham Risk Score, on top of coronary heart disease.
The Seven Countries Study is an epidemiological longitudinal study directed by Ancel Keys at what is today the University of Minnesota Laboratory of Physiological Hygiene & Exercise Science (LPHES). Begun in 1956 with a yearly grant of US$200,000 from the U.S. Public Health Service, the study was first published in 1978 and then followed up on its subjects every five years thereafter.
QRISK3 is a prediction algorithm for cardiovascular disease (CVD) that uses traditional risk factors together with body mass index, ethnicity, measures of deprivation, family history, chronic kidney disease, rheumatoid arthritis, atrial fibrillation, diabetes mellitus, and antihypertensive treatment.
The Caerphilly Heart Disease Study, also known as the Caerphilly Prospective Study (CaPS), is an epidemiological prospective cohort, set up in 1979 in a representative population sample drawn from Caerphilly, a typical small town in South Wales, UK.
Frank B. Hu is a Chinese American nutrition and diabetes researcher. He is Chair of the Department of Nutrition and the Fredrick J. Stare Professor of Nutrition and Epidemiology at the Harvard T.H. Chan School of Public Health, and Professor of Medicine at the Harvard Medical School.
Hypertension is a condition characterized by an elevated blood pressure in which the long term consequences include cardiovascular disease, kidney disease, adrenal gland tumors, vision impairment, memory loss, metabolic syndrome, stroke and dementia. It affects nearly 1 in 2 Americans and remains as a contributing cause of death in the United States. There are many genetic and environmental factors involved with the development of hypertension including genetics, diet, and stress.
Ioanna Tzoulaki is a professor of Chronic Disease Epidemiology at Imperial College London. She investigates prognostic risk factors and models for chronic diseases and meta-epidemiology. In 2019 she received a Greek L’ORÉAL-UNESCO Award for Women in Science.
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