What is the role of geography in the etiology of multiple sclerosis (MS)?

Updated: Oct 08, 2019
  • Author: Christopher Luzzio, MD; Chief Editor: Jasvinder Chawla, MD, MBA  more...
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Answer

Geography is clearly an important factor in the etiology of MS. The incidence of the disease is lower in the equatorial regions of the world than in the southernmost and northernmost regions. However, a systematic review by Alonso and Hernán found that this latitude gradient became attenuated after 1980, apparently due to an increased incidence of MS in lower latitudes. [38]

Apparently, whatever environmental factor is involved must exert its effect in early childhood. If an individual lives in an area with low incidence of MS until age 15 years, that person's risk remains low even if the individual subsequently moves to an area of high incidence.

On the other hand, certain ethnic groups (eg, Eskimos), despite living in areas of higher incidence, do not have a high frequency of MS. Therefore, the exact role played by geography versus genetics is not clear.


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