Geography in multiple sclerosis.

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.