Regional variations in the incidence of end-stage renal failure in Japan

Context Despite recent medical advances, the number of patients beginning dialysis annually is increasing in both the United States and Japan. The ethnically homogeneous population of Japan presents an opportunity to study the presence of factors other than race/ethnicity that might contribute to incidence of end-stage renal disease (ESRD), Objective To determine if and where regional differences exist in ESRD in Japan. Design, Setting, and Subjects Analysis of data reported by the Japanese Society for Dialysis Therapy based on the annual number of patients with ESRD beginning maintenance dialysis therapy in all 47 prefectures of Japan from 1982 to 1998. Main Outcome Measures Mean annual ESRD incidence and increasing rate of ESRD in each of 11 predefined areas making up the entire country. Results Incidence of ESRD increased approximately 3-fold in Japan during the study years, from 81.3 per 1 million in 1982 to 237.6 per 1 million in 1998. Significant regional differences were found in both measures. The mean (SEM) annual ESRD incidence (P<.01) and increasing rate of ESRD (P<.01), respectively, were significantly different across Japan. Koshinetsu (140 [11] per 1 million and 9.1 [0.6] per 1 million/y) and Hokuriku (141 [12] per 1 million and 9.7 [0.5] per 1 million/y) were the areas with the lowest incidence and increasing rate of incidence, while Okinawa (188 [17] per 1 million and 13.4 [0.6] per 1 million/y) and Kyushu (179 [15] per 1 million and 12.0 [0.6] per 1 million/y) were the areas with the highest incidence and increasing rate of incidence. Conclusions We found definite and significant regional differences in incidence and increasing rate of incidence of ESRD in Japan. Further analyses are needed to identify factors that contribute to these regional differences and thereby improve strategies for treatment of renal disease.