Accumulation of adverse socioeconomic position over the entire life course and the risk of myocardial infarction among men and women: results from the Stockholm Heart Epidemiology Program (SHEEP).

BACKGROUND: Accumulation of adverse socioeconomic position over the life course is assumed to increase the risk of myocardial infarction.
OBJECTIVE: To analyse in detail whether the accumulation of adverse socioeconomic position over the life course increases the risk of myocardial infarction, using yearly information on individual socioeconomic position from birth to disease onset.
DESIGN: Case-control study of risk factors for incident myocardial infarction (Stockholm Heart Epidemiology Program).
SETTING: All Swedish citizens born during 1922-49 and living in Stockholm County during 1992-4. PARTICIPANTS: 550 female and 1204 male patients and 777 female and 1538 male controls. Every year in manual work was added to calculate a proportion of the whole life course spent in adverse socioeconomic position.
RESULTS: With increasing proportion of life spent in adverse socioeconomic position, we found an increasing risk of myocardial infarction. The relative risk of myocardial infarction was 2.36 (95% confidence interval (CI) = 1.79 to 3.11) for men and 2.54 (95% CI = 1.70 to 3.78) for women who, over the entire life course, had always been in adverse socioeconomic position compared with those who had never been in adversity. We also found a strong increase in risk from being in adversity for only a few years, indicating important selection processes.
CONCLUSIONS: Accumulated experience of adverse socioeconomic position over the entire life course increases the risk of myocardial infarction for men and women, but it is not a pure accumulation process as "how" and "when" the accumulation occurs also seems to have a role. The accumulation effect is partly mediated by the acquisition of health-damaging experiences.