Incidence of myocardial infarction in a general population: the Marshfield Epidemiologic Study Area

Much of what is known about the occurrence of myocardial infarction (MI) in populations is derived from mortality data. International heart disease registries and recent population-based studies provide only limited incidence data from selected areas of the United States.

The Marshfield Epidemiologic Study Area (MESA), a defined geographic region where nearly all residents receive their health care from the Marshfield Clinic and affiliated hospitals, is a resource for estimating disease incidence in a general population. MI incidence rates and time trends from 1992 to 1998 were evaluated in MESA.

A total of 1691 MESA residents had their first MI during the study period (age-adjusted rate, 292.4 per 100,000 per year). Rates in MESA were similar to some, and higher than other, incidence rates reported from US populations. About 20% of first MIs were detected only on death certificates. Overall incidence did not change much over time (-0.4% per year, P = 0.68), although rates declined 2.3% per year among women (P = 0.07).

This is the first report of MI incidence in a general population from Wisconsin. The fairly steady incidence trend and the large number of incident events detected through death certificates demonstrate the continued need for primary prevention.