Effect of immigration on multiple sclerosis female to male ratio in Canada: the Canadian Collaborative Study
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Medical Update Memo
September 9, 2009
Summary
MS is a complex disease in which genes and environment play a role. MS affects more women than men, especially in countries such as Canada where there is a higher prevalence of MS. Canadian researchers Drs. Dessa Sadovnick (University of British Columbia) and George Ebers (Oxford University UK) and colleagues report on a Canadian study investigating whether the country of origin and age of migration has an impact on the female to male ratio of MS incidence. J Neurol Neurosurg Psychiatry. 2009 Aug 25
Details
The female to male ratio for multiple sclerosis seems to be increasing over time. Amongst immigrants with MS researchers found that the proportion of females was higher in people from countries of high latitude and the proportion of females was higher when the age of migration was below 21. These findings suggest that the environment plays a very important role in the female sex predominance of MS.
The ratio of female to male MS cases varies geographically, generally being greater in areas of high prevalence. In many regions, including Canada, rising MS incidence in women has been implied by the marked increase in female to male ratio.
Researchers examined the female to male ratio over time in MS patients in the Canadian Collaborative Study born outside of Canada, with MS onset occurring post-migration (n=2531). MS sex ratio in immigrants to Canada is increasing but variable by region of origin and influenced by age at migration. The findings highlight the importance of environmental effect(s) in MS risk, which may prove to be gender-specific.
National Research and Programs
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Disclaimer
The Multiple Sclerosis Society of Canada is an independent, voluntary health
agency and does not approve, endorse or recommend any specific product or therapy,
but provides information to assist individuals in making their own decisions.
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