The prevalence and clinical characteristics of MS in northern Japan

Area of Science:

• Neurology
• Epidemiology
• Neuroimmunology

Background:

• Multiple sclerosis (MS) has a low prevalence in Japan, with a notable frequency of the optic-spinal form (OS-MS).
• No intensive epidemiological studies on MS prevalence in Japan have been conducted for over 30 years.
• Previous research indicated a relatively high OS-MS frequency in Japan compared to Western countries.

Purpose of the Study:

• To conduct a province-wide prevalence study of MS in the Tokachi province of Hokkaido, Japan.
• To determine the current prevalence rate of MS and compare clinical features with other Japanese and Western populations.
• To investigate the frequency of the optic-spinal form of MS in this region.

Main Methods:

• A prevalence study of MS was conducted in Tokachi province, Hokkaido, as of March 31, 2001.
• Case ascertainment utilized data from 13 hospitals treating neurological diseases, including MS.
• Patients were classified using Poser's criteria for clinically definite or laboratory-supported definite MS (LSDMS).

Main Results:

• The prevalence rate of LSDMS in Tokachi province was 8.57 per 100,000 (31 cases out of 361,726 individuals).
• The male/female ratio was 1:2.9, with a mean age at onset of 29.1 years.
• Of the 31 MS patients, 5 (16%) were classified as OS-MS, a lower frequency than previously reported in Japan.

Conclusions:

• The prevalence of MS in Hokkaido's Tokachi province is the highest reported among Orientals to date, though still lower than in Western countries.
• Contrary to prior Japanese studies, the frequency of the optic-spinal form of MS was relatively low in Hokkaido.
• This study highlights regional variations in MS epidemiology within Japan and provides updated prevalence data.