Age-related incidence and other epidemiological aspects of myelodysplastic syndromes.

Although most haematologists perceive a rising prevalence and incidence of myelodysplastic syndromes (MDS), reliable epidemiological data on these disorders are largely lacking. The bone marrow register of the University of Düsseldorf allowed us to assess among other epidemiological features the incidence of MDS, which was compared to that of acute myeloid leukaemia (AML). Among a total of 18,416 different patients registered between 1975 and 1990, 584 cases of MDS (3.2%) and 506 cases of AML (2.8%) were identified. Over the study period, the percentage of newly diagnosed MDS rose from 1.3% to 4.5%, while there was no upward trend for AML. Among all patients undergoing bone marrow biopsy, the proportion of those over 60 years of age increased from 41.9% in 1975 to 54.1% in 1990. We found a strong correlation between the proportion of elderly patients and the relative frequency of MDS diagnoses. Thirty-one patients (5.3%) were classified as a secondary MDS because of previous treatment with cytotoxic chemotherapy and/or irradiation for a variety of malignancies. Twelve patients were identified in whom occupational exposure to organic solvents could not be ruled out. For calculating age-specific incidence rates, the analysis was confined to the town district of Düsseldorf (575,000 inhabitants), because exact demographical data were available for this population. In the last quinquennium of the study period (1986-90), myelodysplastic syndromes were more frequent than AML in the age group 50-70 years (4.9 v 1.8/100,000/year). In patients over 70, the incidence of MDS was more than 3 times that of AML (22.8 v 6.7/100,000). In this group, men had a higher incidence of MDS (33.9/100,000) than women (18/100,000). Crude annual incidence (all age groups) was also higher for MDS (4.1/100,000) than for AML (2.1/100,000) in recent years. We conclude that MDS are relatively common haematological neoplasias. The rising incidence in recent years is probably not due to changes in aetiological factors, but may reflect increased awareness on the part of physicians and extended use of diagnostic procedures in elderly patients.