[Epidemiological study of motor neuron disease in Hokkaido island--its incidence, prevalence and regional distributions--ALS Study Group].

The incidence, prevalence and regional distributions of sporadic motor neuron disease (MND) from 1980 through 1989 were evaluated in collaboration with multiple neurological institutes in Hokkaido island. Patients with sporadic MND were collected from three sources: 1) neurologist practicing in Hokkaido island, 2) sending inquiries to 620 major hospitals, 3) notification file of MND provided by Japanese Ministry of Welfare and Health. Three hundred and eighty-nine patients with sporadic MND were ascertained for this study. Of 389 patients, 238 patients were men and 151 patients were women, and the ratio of men to women was 1.6:1. The mean age of onset was 58.2 +/- 10.3 years old, 57.7 +/- 10.4 for men and 58.9 +/- 10.0 for women. Their clinical presentations were 303 patients with ALS, 52 patients were PBP and 34 patients were SPMA. The crude incidence rate for both sexes combined for 1980 through 1989 was estimated as 0.69 per 100,000 person-year. The age- and sex-adjusted incidence for men was 0.86 per 100,000 person-year (95% CI, 0.75 to 0.97) and that is higher than 0.53 per 100,000 person-year (95% CI, 0.45 to 0.61) for women. The average, crude prevalence rate from 1985 through 1989 was estimated as 2.25 per 100,000 person-year. There are no overall trends of changing the pattern in incidence and prevalence of MND in Hokkaido island, however the geographic distributions of the incidence of MND according to towns and cities disclosed the presence of some relative clustering areas.(ABSTRACT TRUNCATED AT 250 WORDS)