Researchers suggest that latitude and
sex ratio trends in the incidence of multiple sclerosis may
be shifting
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Medical Update Memo
August 18, 2008
Summary
Multiple sclerosis (MS) has been traditionally
considered to be more frequent in women and
in regions more distant from the equator. However,
recent reports suggest that the latitude gradient
could be disappearing and that the female-to-male
ratio among patients with MS has increased
in the last decades. Neurology 2008;71:129–135
Details
Researchers from the University of Minnesota
have conducted a systematic review of incidence
studies of MS to assess the overall incidence
of MS and explore possible changes in the latitude
gradient and the female-to-male ratio over
time.
A review of incidence studies of MS published
in Medline between 1966 and February 2007 was
conducted. Age- and sex-specific incidence
rates were collected from eligible publications.
Differences in rates were assessed according
to latitude and period of case ascertainment.
Additionally, they evaluated the association
between period of case ascertainment and the
female-to-male ratio.
The overall incidence rate of MS was 3.6 cases
per 100,000 person-years. Higher latitude was
associated with higher MS incidence, though
this latitude gradient was attenuated after
1980, apparently due to increased incidence
of MS in lower latitudes. The female-to-male
ratio in MS incidence increased over time,
from an estimated 1.4 in 1955 to 2.3 in 2000.
The latitude gradient present in older incidence
studies of multiple sclerosis (MS) is decreasing.
The female-to-male MS ratio has increased in
the last five decades.
ASK MS Information System Code: 2.3gg
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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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