Incidence of leukemia in Olmsted County, Minnesota, 1975 through 1989.

OBJECTIVE

To determine the incidence of leukemia in Olmsted County, Minnesota, for a recent 15-year period and to compare the data with reported rates for the previous 40 years.

DESIGN

We conducted a population study of leukemia diagnosed between 1975 and 1989 in residents of Olmsted County by review of medical records identified through diagnostic indexes, death certificates, autopsy files, and histologic preparations.

MATERIAL AND METHODS

Diagnoses of leukemia were categorized into various subtypes, and age- and sex-specific incidence rates were calculated for leukemia as a whole and for each subtype. In addition, incidence rates were age- and sex-adjusted to the 1970 US white population for comparison with earlier published rates. Age and annual trends as well as sex differences were assessed with the generalized linear interactive model approach.

RESULTS

During 1975 through 1989, the mean annual incidence rate for leukemia was 12.3 per 100,000 population in Olmsted County. When adjusted for age and sex, the rate per 100,000 was 13.6, in comparison with a similarly adjusted rate of 11.8 for the previous decade (1965 through 1974). The rates for chronic myelogenous leukemia and acute lymphocytic leukemia remained stable throughout the entire study period; however, rates for acute myelogenous leukemia and chronic lymphocytic leukemia increased, most prominently in patients 50 years of age or older. This increased rate occurred in both males and females, but the incidence rates for both subtypes began increasing earlier for males than for females.

CONCLUSION

Although we cannot rule out an actual increase in incidence rates for these types of leukemia in the elderly population, we believe that the increase in persons older than 50 years of age reflects social change in improved health care and its better utilization by elderly persons, as well as the ability to diagnose leukemia earlier than in the past.