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Multiple sclerosis in time and space--geographic clues to cause
1Neuroepidemiology Section, Veterans Affairs Medical Center, Washington DC, USA.
Journal of Neurovirology
|June 29, 2000
Summary
Multiple sclerosis (MS) risk varies geographically, influenced by migration age. A persistent infection, primary multiple sclerosis affection (PMSA), is hypothesized as the cause, with the Faroe Islands offering a unique research setting.
Area of Science:
- Epidemiology
- Infectious Disease Research
- Neurology
Background:
- Multiple sclerosis (MS) exhibits distinct geographical prevalence zones, with high-risk areas concentrated in Europe, North America, and Oceania.
- Migration patterns significantly impact MS risk; individuals migrating after age 15 retain their birth-risk, while younger migrants (ages 11-45) to high-risk areas face increased susceptibility.
- Epidemic occurrences of MS have been documented in North Atlantic islands, notably the Faroe Islands, suggesting a transmissible agent.
Purpose of the Study:
- To analyze the geographical distribution of multiple sclerosis (MS) prevalence.
- To investigate the role of migration age in modulating MS risk.
- To explore the hypothesis of a persistent infectious agent, primary multiple sclerosis affection (PMSA), as the underlying cause of MS, particularly in epidemic settings like the Faroe Islands.
Main Methods:
- Geographical analysis of MS prevalence data across different global regions.
- Epidemiological study of migration patterns and their correlation with MS risk.
- Historical analysis of MS epidemic outbreaks, focusing on the Faroe Islands and potential transmission dynamics.
Main Results:
- MS prevalence varies significantly worldwide, categorized into high (30+/100,000), medium, and low (<5/100,000) frequency zones.
- Migration before age 15 from high to low-risk areas does not alter risk, but migration to high-risk areas between ages 11-45 increases susceptibility.
- The Faroe Islands experienced successive MS epidemics starting in 1943, with a 13-year interval, suggesting a transmissible agent (PMSA) introduced post-WWII.
Conclusions:
- MS acquisition is typically linked to early adolescence, with a long latency period before clinical manifestation.
- The hypothesis of primary multiple sclerosis affection (PMSA) as a precursor infection warrants further investigation, especially in the Faroe Islands where specific regions remain MS-free.
- Understanding geographical risk factors and potential infectious origins is crucial for future MS research and prevention strategies.