Subacute myelo-optico neuropathy (SMON) in Hokkaido, an epidemiological study. I (author's transl)

Abstract

A statistical study was conducted on SMON (subacute myelo-optico neuropathy) in Hokkaido, taking the theory of clioquinol etiology into consideration.Results obtained are following:1. In Hokkaido, SMON began to occur sporadically about 1958, reached epidemic proportions from 1962 to 1966 and then abruptly declined. Up to the end of September, 1972, a total of 433 cases had been confirmed or strongly suspected to be SMON.2. The incidence was highest in the fifth decade of both sexes. The over-all sex ratio was 1:2.1, (i.e. twice as high in females), and progressed with age to 1:5.3 in the eighth decade.3. There were marked regional differences in the incidence of SMON, but these did not reflect population size. However, the incidence was closely related to the presence of medical institutions in which clioquinol was administered in excess to patients with gastrointestinal disorders.4. It was statistically confirmed that the daily dose of clioquinol, the duration of administration of the drug, and the number of persons who received it showed a high correlation with the incidence of SMON. It was noted, however, that the daily dose related to the incidence differed with the medical institution.5. In some areas, the decrease in the occurence of new SMON cases slarted before September, 1970, when the use of clioquinol was officially discontinued. The earlier disappearance of SMON appears to have been due to the reduction in the daily dose of cliquinol prescribed in the medical institutions in these areas.