The frequency of sarcoidosis in Finland and Hokkaido, Japan. A comparative epidemiological study

Finland and Hokkaido resemble each other; the four season climate with cold winters and cool summers is the same as is the frequency of tuberculosis. The size of the population is almost the same. From the 1984 Japanese nationwide sarcoidosis survey we got the data from Hokkaido (288 patients) in order to compare the information with similarly collected data in Finland from 1984 (1,378 patients). The crude prevalence of sarcoidosis was 28.2 per 100,000 in Finland and 3.7 per 100,000 in Hokkaido. The annual incidence was 11.4 per 100,000 in Finland and 1.0 per 100,000 in Hokkaido. The sex distribution was similar; 63% vs 67% women in Finland and Hokkaido, respectively. At diagnosis the Hokkaidoan patients were significantly younger. In Hokkaido more cases were detected via mass X-ray survey (43% vs 34%). Among symptomatic patients eye symptoms were more frequent in Hokkaido, whereas respiratory and joint symptoms and erythema nodosum were more frequent in Finland. Bilateral hilar lymphadenopathy (BHL) was equally distributed (82% vs 84% whereas parenchymal lesions were seen more often in Finland (49% vs 25%) as well as peripheral lymphadenopathy (16% vs 8%).