Incidence of aplastic anemia in Japan: analysis of data from a nationwide registration system
METHODS: The Japanese government has established a nationwide registration system for patients with intractable diseases including aplastic anemia. We utilized data converted to electronic form between 2004 and 2012 for analysis. The data include information on patients’ sex, birth year and onset year. However, only 70 to 80% of all registered patients’ data have been converted to electronic form. We calculated the electronic data entry rate as the number of patients whose data were converted into electronic form divided by the total number of patients enrolled in the registration system for each year. The estimated total number of incident cases in each year was calculated as the sum of the number of incident cases registered in the following years, divided by the entry rate of the registered year.
RESULTS: During the nine years from 2004 to 2012, the estimated total number of incident cases of aplastic anemia was 9,455. The incidence was estimated as 8.2 per 1,000,000 person-years. The male and female incidences were 7.6 and 8.8 per 1,000,000 person-years, respectively. The sex ratio (female/male) was 1.16. The age-specific incidence showed peaks at age 10-20 years and 70-80 years, with a larger peak observed at 70-80 years.
CONCLUSIONS: This is the first report of the incidence of aplastic anemia at the nationwide population level in Japan. It was found that the incidence in Japan is higher than in western populations.
ACKNOWLEDGEMENTS: This study was supported by a Grant-in-Aid for Research Committee on the Idiopathic Disorders of Hematopoietic Organs from the Ministry of Health, Labour and Welfare of Japan.