Ethnic factors in multiple sclerosis: a review and critique of the epidemiological literature.

A review of the international epidemiological literature is undertaken with the view of identifying the main demographic and sociocultural features of MS as they apply to ethnic groups. Ethnic groups are differentiated principally in terms of three variables: race, religion, and nationality. Although MS is present in the three principal racial groups in the world (white, oriental, and black), it tends to be unequally distributed. Four hypotheses are formulated regarding the unequal susceptibility of the races to MS. Hypothesis 1. Whereas the highest MS rates are found in regions of the world inhabited largely by white populations, the lowest rates tend to be found in those areas where non-whites live. Hypothesis 2. Racially different groups living in the same geographical area tend to have different MS rates, although there is tendency for whites to experience MS more often than non-whites. The data associated with hypotheses 1 and 2 support a uniformly higher and lower risk for MS among respectively whites and non-whites. If these findings are valid, these studies indicate that racial (genetic) factors may play an important role in the distribution of this disease. Hypothesis 3. Data from this hypothesis confirm the proposition that the risk of MS among white and non-white populations tends to be variable, with variability in susceptibility being especially prominent among whites. Hypothesis 4. The prevalence data, plus the geographical distributions, in the US serve to support the firmly established interpretation that prevalence in all three racial groups tends to increase in frequency with increasing geographical latitude.(ABSTRACT TRUNCATED AT 250 WORDS)