Objective: Age adjusted incidence of myocardial infarction has been found to vary substantially between the residential areas of the city of Malmö. The objective of this study was to assess the extent to which major biological risk factors and socio-economic circumstances account for the differences in incidence of and mortality from myocardial infarction.
Design: Ecological study of risk factor prevalence and incidence and mortality from myocardial infarction.
Setting: Seventeen administrative areas in Malmö, Sweden.
Subjects: Assessment of risk factor prevalence was based on 28 466 men and women, ranging from 45 to 73 years old, who were recruited as participants in the Malmö Diet and Cancer study. Information on serum lipids was available in a random subsample of 5362 subjects. Information about socio-economic level of the residential area was based on statistics from the Malmö City Council and Statistics Sweden.
Main outcome measures: Weighted least square regressions between prevalence of risk factors (i.e. smoking, hypertension, obesity, diabetes, hypercholesterolemia and hypertriglyceridemia), a myocardial infarction risk score, a socio-economic score and incidence and mortality from myocardial infarction.
Results: The risk factor prevalence and myocardial infarction incidence was highest in areas with low socio-economic level. Prevalence of smoking, obesity and hypertension was significantly associated with myocardial infarction incidence and mortality rates amongst men (all r > 0.60). Prevalence of smoking was significantly associated with incidence and mortality from myocardial infarction amongst women (r = 0.66 and r = 0.61, respectively). A myocardial infarction risk score based on four biological risk factors explained 40-60% of the intra-urban geographical variation in myocardial infarction incidence and mortality. The socio-economic score added a further 2-16% to the explained variance.
Conclusion: In an urban population with similar access to medical care, well-known biological cardiovascular risk factors account for a substantial proportion of the intra-urban geographical variation of incidence of and mortality from myocardial infarction. The socio-economic circumstances further contribute to the intra-urban variation in disease.