Prefectural difference in spontaneous intracerebral hemorrhage incidence in Japan analyzed with publically accessible diagnosis procedure combination data: possibilities and limitations

OBJECTIVES: Annually reported, publically accessible Diagnosis Procedure Combination (DPC) data from the Japanese government is a part of the total DPC database of the Japanese medical reimbursement system for hospitalization. Although medical issues can be evaluated with these data promptly, the applicability of these data in epidemiological analyses has not been assessed. METHODS: We performed analyses using only statistical indices reported on the a government website. As a preliminary step, the prefectural consistency of spontaneous intracerebral hemorrhage (sICH) was examined with prefectural mortality over 20 years. Then the prefectural incidence of sICH for four years was calculated, utilizing publically accessible DPC data. To determine its reliability, the consistency was examined, and correlations were analyzed with three prefectural factors expected to have an effect: the elderly rate, mortality due to sICH, and the non-DPC bed rate. In addition, a comparison model between prefectures with this method was developed by analyzing other prefecture-specific factors. RESULTS: Prefectural mortality due to sICH and prefectural sICH incidence in the DPC database were both consistent over the years. Prefectural sICH incidence had a constant positive correlation with the elderly rate, a partial correlation with mortality due to sICH, but no correlation with the non-DPC bed rate, which is one of the major biases when utilizing the DPC database. In the comparison model, the factors of low income and alcohol consumption showed increased sICH incidence. CONCLUSIONS: Although careful attention to its limitations is required, publically accessible DPC data will provide insights into epidemiological issues.