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Abstract:
Both mortality and morbidity data indicate quite clearly that multiple sclerosis is a geographically-related disease, and thus MS can be thought of as an acquired environmental (exogenous) illness. High frequency parts of the world for MS are Europe between 65 degrees and 45 degrees north latitude, northern United States and southern Canada, New Zealand, and southern Australia. These regions are bounded by medium frequency MS regions: in Europe to the north, east, and south; in America for southern U.S.; and the remainder of Australia. Latin America, Asia and Africa are essentially of low frequency from present data. Latitude is not a sufficient criterion: at 40 degrees north latitude, MS is high in America, medium in Europe, and low in Asia. All high and medium risk areas therefore are in Europe or European colonies; thus MS is the white man's burden spread from western Europe. Within the U.S., MS is less common among Negroes, Japanese, and possibly Amerindians than in whites regardless of geography. Migration studies among risk areas indicate that migrants keep much of the risk of their birthplace, but also that overall the risk is decreased by high-to-low migration, and probably increased by low-to-high. For the former, it seems that adolescence is the age critical for retention of birthplace risk. Some preliminary data on a possible epidemic of MS are also presented. All the epidemiologic information would be most easily explained if MS were an infectious (viral) illness with prolonged latency. The proof of this though must come from the laboratory.
Insights
Multiple sclerosis (MS) is a geographically-related disease, predominantly affecting people of European descent in higher latitudes. Migration studies suggest environmental factors play a key role, possibly infectious agents.
Area of Science:
- Epidemiology
- Environmental Health
Background:
- Multiple sclerosis (MS) exhibits clear geographical patterns in mortality and morbidity.
- High-frequency MS regions include Europe (45-65 degrees N latitude), northern US, southern Canada, New Zealand, and southern Australia.
- Low-frequency areas include Latin America, Asia, and Africa, indicating environmental influences.
Purpose of the Study:
- To analyze the geographical distribution of multiple sclerosis.
- To investigate the role of environmental factors and migration in MS risk.
- To explore the hypothesis of an infectious etiology for MS.
Main Methods:
- Analysis of global mortality and morbidity data for multiple sclerosis (MS).
- Examination of geographical risk variations, including latitude and regional differences.
- Review of migration studies to assess the impact of birthplace and environmental changes on MS risk.
Main Results:
- MS prevalence is highest in temperate regions of Europe and European colonies, with latitude being a significant, but not sole, determinant.
- Populations of European descent are disproportionately affected; MS is less common in Black, Japanese, and Indigenous American populations in the US.
- Migration studies indicate that birthplace risk is retained, particularly if migration occurs before adolescence, suggesting early-life environmental exposures are critical.
Conclusions:
- Multiple sclerosis (MS) is strongly linked to environmental factors, likely acquired and exogenous.
- The observed epidemiological patterns are most consistent with an infectious (viral) cause with a long incubation period.
- Further laboratory research is required to confirm the infectious etiology of MS.