Descriptive Epidemiology of Amyotrophic Lateral Sclerosis in Japan, 1995-2001

BACKGROUND: This study was conducted to describe the epidemiologic features of amyotrophic lateral sclerosis (ALS) in Japan by examining annual trends in mortality (1995-2001), and to discuss the background factors possibly responsible for the recent variations in the mortality rate. METHODS: Trends in both the age-adjusted and age-specific mortality rates of ALS were examined by using the data obtained from the vital statistics of Japan between 1995 and 2001. RESULTS: There were small increases in the number of ALS deaths (from 1249 to 1400 per year) and the crude mortality rates (from 1.00 to 1.10 per 100,000 population) between 1995 and 2001. The age-adjusted mortality rate of ALS (adjusted using the 1985 model population of Japan) has decreased (from 0.84 per 100,000 population in 1995 to 0.74 in 2001). Age-specific mortality rates have been increasing particularly in the population older than 70 years of age, with the peak in mortality in the 70- to 80-year old age group. CONCLUSIONS: ALS mortality rates increased proportionally more for elderly population during the study period. Further epidemiologic studies will be needed to clarify the possible background factors contributing to the increase in ALS mortality in the elderly.