Fast track — ArticlesAssociation of psychosocial risk factors with risk of acute myocardial infarction in 11 119 cases and 13 648 controls from 52 countries (the INTERHEART study): case-control study
Introduction
Popular opinion holds that stress is an important risk factor for coronary heart disease. However, compared with other major risk factors, psychosocial variables such as stress are difficult to define objectively, and stress consists of several different (and inter-related) elements. Therefore, measurement of stress is complex and difficult. Despite this drawback, several constructs within the broad conceptual framework of stress are increasingly regarded as being causally related to coronary heart disease.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
The concept of stress encompasses several factors, from external stressors such as job stress,5, 8, 10, 13 adverse life events7 and financial problems, to potential reactions to stress such as depression,1, 2, 3 vital exhaustion,15 anxiety,12, 14 psychological distress,11 and sleeping difficulties. The same construct might not be applicable in different countries and ethnic groups, because cultural influences can vary. Perceived mental stress, measured by response to a single-item question, was associated with increased mortality from coronary disease in a large study of Japanese men and women.9 Apart from this study,9 previous investigations have been done in mainly North American or European populations. Thus, limited data are available about psychological variables and coronary heart disease in other countries and ethnic groups. The aim of the INTERHEART study, undertaken in a large number of patients with a first acute myocardial infarction and controls matched for age and sex, was to investigate the associations of several psychosocial stressors with the risk of acute myocardial infarction globally, and in different populations characterised by age, sex, geographic region, and ethnic origin.
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Study Population
12461 incident cases of acute myocardial infarction from 262 centres in 52 countries representing all geographic regions, and 14637 age-matched, sex-matched, and site-matched controls free of clinical heart disease, took part in the study.16, 17 Centres attempted to recruit consecutive patients. Recruitment was from February, 1999, until March, 2003. Patients admitted to the coronary care unit or equivalent cardiology ward of participating centres were screened to identify incident cases of
Results
The mean age of cases was 58·2 years (SD 12·2) and of controls 57·1 years (12·1); 24·2% (2686) of cases and 26·5% (3619) of controls were women. Figure 1 outlines the distribution of cases and controls by region and ethnic origin and provides the odds ratios associated with high general stress. We defined high general stress as several periods of or permanent stress, at work, home, or both. Figure 2 shows corresponding data for depressive mood, which we defined as feeling sad, blue, or
Discussion
Our study shows that several elements reflecting psychosocial stress are associated with increased risk of acute myocardial infarction. These factors include those that are subjective and perceived by the patients, such as stress, defined as tension or anxiety due to external influences. Some of these measures—eg, locus of control or depression—are not generally perceived by lay people to be stressors. Further, discrete external events (eg, major life events), which are less subjective and less
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