Work related stressful life events and the risk of myocardial infarction. Case-control and case-crossover analyses within the Stockholm heart epidemiology programme ( SHEEP)

Study objectives: Recent changes in labour market conditions and in the organisation of work in developed societies have increased exposure to work related stress. The question is whether this also implies an increased risk of myocardial infarction, either through the triggering effect of acute stress, or through accumulation of stress over several months. Design: A case-control and a case-crossover study design was applied. Setting: The Stockholm heart epidemiology programme ( SHEEP), in Stockholm County during 1992 to 1994. Participants: Patients with a first episode of non-fatal acute myocardial infarction, a total of 1381 men and women, responded to questionnaires and participated in interviews and health examinations. Main results: The case-crossover analysis showed triggering effects of sudden, short term situations of increased work load or work competition. Having had a high pressure deadline at work'' entailed a sixfold increase in risk of myocardial infarction ( OR = 6.0 95% CI ( 1.8 to 20.4)) during the next 24 hours. The importance of work related life events as risk factors for myocardial infarction was supported by the case-control analysis. However, no support was found for the hypothesis that an accumulation of stressful life events over a period of 12 months increases the risk of myocardial infarction. Conclusion: Specific work related stressful life events seem to be potential triggers of the onset of myocardial infarction.