Associations between classical cardiovascular risk factors and coronary artery disease in two countries at contrasting risk for myocardial infarction: the PRIME Study

Abstract

Purpose: In two countries with contrasting risk for coronary artery disease (CAD)—Northern Ireland and France—a case-control study was performed on baseline data within a cohort study to compare the strength of the associations between CAD prevalence and classical risk factors. Method and results: A sample of 9561 men, aged 50–60 years, was studied: 382 had had myocardial infarction or angina, and 9179 were controls. In both countries, variables associated with CAD were age, body mass index, hypertension, diabetes, family history of myocardial infarction (MI), tobacco consumption, triglycerides, HDL-cholesterol, apolipoprotein A-I and B levels. Logistic regression analyses were conducted using standardized odds ratios. The strength of the associations with CAD was rather similar in the two countries (Northern Ireland versus France) for age [1.26 (1.10–1.45) vs. 1.41 (1.17–1.69)], family history of MI [1.50 (1.04–2.15) vs. 1.83 (0.99–3.37)], hypertension [1.49 (1.13–1.97) vs. 1.67 (1.14–2.44)], diabetes [5.42 (2.53–11.60) vs. 2.24 (1.06–4.73)], tobacco consumption [1.43 (1.27–1.60) vs. 1.39 (1.22–1.58)], HDL-cholesterol [0.80 (0.68–0.94) vs. 0.86 (0.70–1.06)] and triglyceride levels [1.17 (1.01–1.36) vs. 1.10 (0.91–1.32)]. Discrepancies concerned lipoprotein(a) [1.22 (1.06–1.40) vs. 0.96 (0.81–1.15), P<0.01], with stronger associations in Northern Ireland than in France. Conclusion: It is concluded that the higher prevalence of CAD in Northern Ireland cannot be explained by major differences in the susceptibility to classical risk factors; the difference in risk of CAD appears mainly related in Northern Ireland to other risk factors including a worse lipid profile and genetic/environmental interactions.

Introduction

Since the 1970s, epidemiological studies have demonstrated large international differences in coronary artery disease (CAD) incidence and mortality rates [1], [2]. Several risk factors have been identified, and international surveys have been planned in order to investigate these cross-cultural differences in CAD morbidity and mortality [3], [4]. Results, however, have shown that the measures of classical risk factors at a population level only explain part of this variability [5], [6], [7]. Further research was thus necessary, and it was aimed at the identification of new additional risk factors for CAD [8], [9], [10]. Lipoprotein(a), for example, was the focus of intensive research, and led to conflicting results in its association with CAD in populations [11], [12], [13], [14]. Despite the emergence of such novel factors we have tried to assess the role of classical risk factors in explaining these intercountry differences in CAD risk [15], [16], [17], [18].

The PRIME Study [19] (Prospective Epidemiological Study of Myocardial Infarction (MI)) is a prospective cohort study, designed to evaluate the contribution of nutritional, metabolic and genetic risk factors in the development of ischemic heart disease in Europe, with emphasis on those factors which might partially explain the incidence variability. The 5-year follow-up of the male cohorts enrolled in France and in Northern Ireland will be available in the year 2001. The description of the population under study has already been published, and it was shown that estimates of the individual’s chance of developing a major CAD event calculated from available multiple logistic functions scores, combining age, cigarette smoking, blood pressure, total cholesterol and body mass index, were of the same order of magnitude in Belfast, Lille and Strasbourg, slightly higher than in Toulouse [19]. Using the baseline data from The PRIME Study, a case-control study was carried out to determine whether a higher prevalence of CAD in Northern Ireland than in France could be explained by a difference in the susceptibility to risk factors. Our aim was to compare the strength of associations between prevalence of CAD morbidity and the prevalence of classical risk factors (an extended list of CAD risk factors in comparison with the previous work [19]), with identical methodology and unique data set, in two European neighboring countries at contrasting risk for CAD.