Multiple sclerosis in a migrant population: 2. Half-orientals immigrating in childhood.

We studied offspring of Vietnamese mothers and French fathers who had been born in Vietnam and brought to France to be raised. All but 72 of 3,451 such individuals completed background and neurological questionnaires. Those with positive answers on the latter were examined neurologically. The median year of birth for the 3,379 respondents was 1948, the median year of arrival in France was 1957, and they had resided in France a median of 18 years before interview in 1975. Twenty-five persons had neurological symptoms, and 6 others reported a history of seizures alone. A total of 16 reported seizures: 7 with infantile febrile fits and 9 with afebrile seizure disorders. Three cases of exacerbating-remitting multiple sclerosis (MS) were discovered as well as 3 persons in whom MS was suspected: 1 with cervical myelopathy, 1 with progressive paraparesis, and 1 with bilateral optic neuropathy. The 3 MS cases provided a crude prevalence rate (or 18-year cumulative risk) of 89 per 100,000. Their age-specific prevalence rate was 169 per 100,000 population aged 20 through 29 years. Each measure was similar to such rates for Denmark and had lower 95% confidence limits that clearly exceeded expectations for Vietnam. The results provide further evidence that the risk of MS can be increased by migration in childhood from low- to high-risk regions.