LACK OF REGIONAL VARIATION IN IDDM RISK IN JAPAN

OBJECTIVE - To examine the intracountry variation of IDDM incidence in Japan and compare it with data from the British Isles and the U.S. RE SEARCH DESIGN AND METHODS- IDDM incidence was determined with a standa rdized registry approach in five geographically different areas in Jap an (Hokkaido, Tokyo, Yokohama, Osaka, and Kagoshima) with a total at-r isk population < 15 yr of age of 4.4 million. Data collection was comp leted under the guidelines of the World Health Organization DiaMond pr oject. RESULTS - The incidence and patterns of disease were remarkably similar across the five environmentally different areas. Incidence ra tes per 100,000 were very low and almost identical from northern to so uthern Japan (Hokkaido, 2.07; Tokyo, 1.65; Yokohama, 1.66; Osaka, 1.78 ; and Kagoshima, 1.93). This remarkably low intracountry variation of 0.4/100,000 stands in sharp contrast with the 13.0/100,000 regional va riation in the British Isles and the 10.6/100,000 variation in the U.S . CONCLUSIONS - The results suggest that the remarkable genetic homoge neity in Japan may produce uniformity of incidence.