Epidemiology of Amyotrophic Lateral Sclerosis, Myasthenia Gravis, Multiple Sclerosis and Spino-Cerebellar Degeneration in Tottori Prefecture Japan; A Prevalences Are Rising

Masayoshi Kusumi, Kenji Nakashima, Hideaki Harada, Hideaki Nakayama* and Kazuro Takahashi

Division of Neurology, Institute of Neurological Sciences and *Department of Hygiene, Faculty of Medicine, Tottori University, Yonago 683, Japan

A study of the prevalence of amyotrophic lateral sclerosis (ALS), myasthenia gravis (MG), multiple sclerosis (MS) and spino-cerebellar degeneration (SCD) was conducted in Tottori Prefecture in 1994, and the data were compared with those of similar studies performed in 1974-1987. On the prevalence day, April 1, 1994, a total of 31 patients for ALS, 89 for MG, 34 for MS, 111 for SCD were found to be living in the investigated area, which had a population of 614,410. The prevalence per 100,000 population was 5.0 for ALS, 14.5 for MG, 5.5 for MS and 18.1 for SCD, and the incidence during the period 1988 through 1992 was 1.14 for ALS, 0.91 for MG, 0.52 for MS and 0.84 for SCD per 100,000 population per year. The age- and sex-adjusted prevalence for SCD per 100,000 population was 13.4 in 1994 and 10.2 in 1987, as calculated using the 1985 Japanese population as the standard population. The prevalence of these diseases therefore increased. These results suggest that changes in the age structure of the population and improvements in the treatment of such diseases were the main contributors to the increased prevalence of these diseases.

Key words: aging; incidence; prevalence

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