¹ Department of Epidemiology and Health Promotion (MONICA Data Centre), KTL-National Public Health Institute, Helsinki, Finland
² The Medical School, The University of Manchester, Manchester, UK
³ School of Population Health, Faculty of Health Sciences, University of Queensland, Herston, Australia
⁴ Department of Epidemiology and Public Health, Queens University of Belfast, Belfast, UK

Correspondence to:
Markku Mähönen MD
Department of Epidemiology and Health Promotion, KTL-National Public Health Institute, Mannerheimintie 166, FIN-00300 Helsinki, Finland; markku.mahonen.ktl.fi

Background: Cohort studies have shown that smoking has a substantial influence on coronary heart disease mortality in young people. Population based data on non-fatal events have been sparse, however.

Objective: To study the impact of smoking on the risk of non-fatal acute myocardial infarction (MI) in young middle age people.

Methods: From 1985 to 1994 all non-fatal MI events in the age group 35–64 were registered in men and women in the WHO MONICA (multinational monitoring of trends and determinants in cardiovascular disease) project populations (18 762 events in men and 4047 in women from 32 populations from 21 countries). In the same populations and age groups 65 741 men and 66 717 women participated in the surveys of risk factors (overall response rate 72%). The relative risk of non-fatal MI for current smokers was compared with non-smokers, by sex and five year age group.

Results: The prevalence of smoking in people aged 35–39 years who experienced non-fatal MI events was 81% in men and 77% in women. It declined with increasing age to 45% in men aged 60–64 years and 36% in women, respectively. In the 35–39 years age group the relative risk of non-fatal MI for smokers was 4.9 (95% confidence interval (CI) 3.9 to 6.1) in men and 5.3 (95% CI 3.2 to 8.7) in women, and the population attributable fractions were 65% and 55%, respectively.

Conclusions: During the study period more than half of the non-fatal MIs occurring in young middle age people can be attributed to smoking.

Abbreviations: ACC, acute coronary care; CHD, coronary heart disease; CI, confidence interval; ISIS, international studies of infarct survival; MI, myocardial infarction; MONICA, multinational monitoring of trends and determinants in cardiovascular disease: WHO, World Health Organization

Keywords: epidemiology; risk of non-fatal myocardial infarction; population based studies

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