INTERHEART

INTERHEART
Title	INTERHEART
Type	Case–control study
Field	Cardiology, Epidemiology
Start	1999
Completed	2004
Principal investigator	Salim Yusuf
Locations	Global
Participants	~15,000 cases, ~14,000 controls
Published	2004

INTERHEART INTERHEART was a large, international case–control study of acute myocardial infarction led by Salim Yusuf that aimed to quantify modifiable risk factors across diverse populations. The study enrolled participants from multiple regions including North America, Europe, South America, Africa, South Asia, East Asia, and the Middle East and produced widely cited analyses influencing guidelines from organizations such as the World Health Organization and the American Heart Association. It combined clinical, behavioral, and biochemical data to evaluate population-attributable risks and global patterns of myocardial infarction.

Background

INTERHEART was conceived amid rising cardiovascular disease burdens documented by institutions like the World Health Organization, the Centers for Disease Control and Prevention, and the International Society and Federation of Cardiology. The project was coordinated through academic centers including McMaster University, the Population Health Research Institute, and collaborators in countries represented by institutions such as the All India Institute of Medical Sciences, the Chinese Academy of Medical Sciences, and the University of the West Indies. Funding and oversight involved bodies like the Canadian Institutes of Health Research and philanthropic partners; ethical approvals were obtained from local institutional review boards including those at the University of Toronto and King’s College London.

Methods

INTERHEART used a standardized case–control design recruiting acute myocardial infarction cases from hospitals such as Mount Sinai Hospital and Royal Brompton Hospital and community controls matched by age and sex drawn from centers like Aga Khan University and Charité–Universitätsmedizin. Data collection included questionnaires adapted from instruments used by the Framingham Heart Study, the Nurses’ Health Study, and the MONICA Project, physical measurements similar to those in the Bogalusa Heart Study and biochemical assays processed in reference laboratories affiliated with Harvard Medical School and Johns Hopkins University. Statistical analyses employed multivariable logistic regression techniques developed in epidemiology texts and software from SAS Institute and StataCorp to estimate odds ratios, population-attributable risk, and effect modification across strata by region and sex.

Main Findings

INTERHEART reported that nine potentially modifiable risk factors accounted for the majority of the population-attributable risk for first myocardial infarction worldwide, with consistent effects across regions including South Asia, Sub-Saharan Africa, Latin America, East Asia, and Europe. The study highlighted strong associations between myocardial infarction and factors such as smoking, abnormal lipids, hypertension, diabetes mellitus, obesity measures, physical inactivity, psychosocial stress, alcohol consumption patterns, and dietary factors, producing results that were cited by journals like The Lancet and cited in reports from the World Heart Federation and the American College of Cardiology. Findings influenced clinical practice guidelines from organizations including the European Society of Cardiology and policymaking discussions at the United Nations and the World Health Assembly.

Risk Factors Assessed

INTERHEART assessed tobacco use with instruments comparable to those used in the Global Adult Tobacco Survey and surveillance programs at the World Health Organization, measured lipid fractions including apolipoprotein ratios paralleling assays in the Lipid Research Clinics and the National Cholesterol Education Program, evaluated hypertension using criteria from the Joint National Committee and the International Society of Hypertension, and documented diabetes using self-report and glucose measures consistent with International Diabetes Federation and American Diabetes Association definitions. Additional assessments included anthropometry referencing protocols from the National Health and Nutrition Examination Survey, dietary patterns with methods akin to those in the Mediterranean Diet studies and the PURE study, physical activity measures related to WHO STEPwise approaches, and psychosocial stress instruments similar to those applied in the Whitehall Study and INTERHEART collaborators’ prior work.

Impact and Significance

The INTERHEART study informed global cardiovascular prevention strategies promoted by the World Health Organization, the World Heart Federation, and national bodies such as Health Canada and Public Health England, and it shaped risk communication in guidelines from the American Heart Association and the European Society of Cardiology. Its cross-regional findings were incorporated into subsequent cohort investigations including the Prospective Urban Rural Epidemiology (PURE) study and meta-analyses by the Cochrane Collaboration, and it influenced policy dialogues at the United Nations General Assembly and the World Health Assembly concerning noncommunicable diseases. The study also stimulated research at institutions like Imperial College London, the University of California, San Francisco, and the University of Sydney into implementation science and population-level interventions.

Criticism and Limitations

Critiques of INTERHEART appeared in commentaries by scholars affiliated with universities such as Harvard, Oxford, and the London School of Hygiene & Tropical Medicine, noting inherent limitations of the case–control design relative to cohort studies like the Framingham Heart Study or Nurses’ Health Study. Concerns included potential recall bias in self-reported exposures similar to issues raised in epidemiology critiques at Johns Hopkins and concerns about residual confounding discussed in methodological literature from the University of Cambridge and Yale University. Other limitations cited by analysts at institutions such as McGill University and the University of Queensland included limited temporal inference compared with prospective cohorts, heterogeneity in hospital-based recruitment across sites such as tertiary centers in Mumbai and Lagos, and challenges in generalizing biomarker cutoffs standardized in laboratories like Mayo Clinic and Karolinska Institutet.

Category:Cardiology studies