Measuring disease frequency in the Marshfield Epidemiologic Study Area (MESA).

The Marshfield Epidemiologic Study Area (MESA) is a rare resource for population-based health and medical research developed at Marshfield Clinic Research Foundation. Because of high population coverage and health event capture, MESA is particularly useful for determining the frequency of disease in the general population. A substantial proportion of MESA-based publications appearing in the peer reviewed literature have reported incidence or prevalence rates of disease or disease-related factors. This paper reviews the first 10 years of MESA's support of meaningful inquiry into the frequency of disease occurrence, and briefly reports on the data and methods used for such calculations using selected chronic diseases as examples. Limitations of MESA estimates are discussed as are alternate methods. Compared to limited data published for the selected conditions, occurrence rates in MESA based on diagnostic codes and general validation rules only appear somewhat high, although the observed temporal trends and relationships with demographics are consistent. Rich clinical data sources are available to be linked with MESA to improve the specificity of case ascertainment, as is typically done for disease-specific publications from MESA.