Job strain, social support at work, and incidence of myocardial infarction

Objectives - The combination of high psychological job demands and low decision latitude (high job strain) has been associated with an increased risk of coronary heart disease. It has been proposed that this may also be the case for low social support at work. The aim of this study was to analyse the relations between these psychosocial factors and incidence of myocardial infarction. Methods - Associations between psychosocial work characteristics and incidence of myocardial infarction was investigated through a population based case-control study. The study base comprised employed men and women in five Swedish counties during the years 1976-84. Cases of first myocardial infarction were identified from hospital discharge registers and death records from outside hospital, controls were selected through a random sample, and psychosocial work environment was assessed through a job exposure matrix on the basis of the occupation in the 1970 and 1975 censuses. Results - An increased incidence of myocardial infarction was found for men and women in occupations characterised by low decision latitude. For men this increase was seen primarily in combination with high psychological demands (high job strain) and low social support at work. Younger men (30-54 years of age) in occupations with both high job strain and low social support at work had a relative risk of 1.79 (95% confidence interval (95% CI) 1.22 to 2.65) compared with subjects in low strain and high social support jobs after controlling for age, county of residence, and socioeconomic group. Conclusions - Our results indicate that jobs characterised by low decision latitude, high job strain, or low social support at work may be associated with an increased risk of acute myocardial infarction. If these associations are causal they may be of substantial importance from the point of view of workers' health.