Further Analysis of INTERHEART: What Do the Data Tell Clinicians?

Arya Sharma, MD


January 19, 2006

In This Article


To address these questions (among others), the largest international study of its kind, INTERHEART, was initiated by Salim Yusuf, MB BS, DPhil, and others at the Population Health Research Institute, McMaster University in Hamilton, Ontario, Canada. The first results were presented over a year ago at the 2004 European Society of Cardiology Congress in Munich, Germany (with almost simultaneous publication of the results in The Lancet and with the slides available online).[1,2] Set up as a retrospective, case-controlled study enrolling more than 27,000 people from 52 countries (representing several major ethnic groups), INTERHEART was the first study with a cross-cultural enrollment of sufficient magnitude and statistical power to test these 2 precepts directly -- and now a predefined subanalysis of INTERHEART[3] has further identified a single, clinically relevant and easily measured variable that is a major prognostic factor for future CVD events.

Although the design and results from INTERHEART have been published and discussed, they bear repeating briefly below, followed by presentation of our subanalysis, which highlights the critical anatomic variable that turns out to be one of the major factors clinicians must assess and address in order to make a significant impact on reducing the worldwide burden of CVD.

INTERHEART was conducted via a study questionnaire, translated into 11 languages, that collected data on demographic factors (country of origin, first language), socioeconomic status (education, occupation, income), lifestyle (tobacco use, physical activity, dietary patterns), and personal and family history of CVD and risk factors (self-reported diabetes and hypertension). These components of the questionnaire were added to previously validated questions included in studies of risk factors for CVD, and the questionnaires were administered by trained staff before patients left the hospital.

The study variable was a history of myocardial infarction (MI), with half of the subjects reporting a history of MI and the other half, without MI, serving as the control group. One immediate statistic was that at baseline the mean age for the first presentation of acute MI was 8-10 years lower in men than in women worldwide and 10 years younger in the Middle East, Africa, and South Asia compared with other regions of the world.

Data on medications (prehospital, in-hospital, and discharge) and interventions were abstracted from charts. Standard physical measurements were done in duplicate by the same examiner for each participant: height, weight, waist and hip circumference, and heart rate. A 20-mL sample of nonfasting blood was drawn from each individual and stored frozen for biochemical analyses, including total cholesterol, high-density lipoprotein (HDL)-cholesterol, and apolipoproteins B (apoB) and A1 (apoA1).

The results of INTERHEART identified 9 variables that accounted for over 95% of the risk for future CVD events ( Table ). The odds ratios shown in the table were adjusted for all other risk factors (a complex statistical adjustment that will not be described here), and globally, all 9 risk factors were significantly associated with occurrence of an acute MI (all P < .0001 except alcohol intake, P = .03)

Of the 9 risk factors in the table, we took abdominal obesity to be of particular interest, and so we undertook further analysis of this as a prognostic factor.


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