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Study reports regional variation
of MS rates across Canada
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Medical Update Memo
October
17, 2005
SUMMARY
Researchers at the University of Calgary reported significant regional differences
among prevalence rates of MS across Canada based on data from the Canadian
Community Health Survey, a population-based general health survey. The study
appeared in the October 2005 issue of the journal Multiple Sclerosis (2005:
11). The study found higher rates in the Prairies and Atlantic Canada. Prevalence
rates ranged from a low of 180 people with MS per 100,000 population in Quebec
to a high of 350 per 100,000 in Atlantic Canada. The regional variations
among MS prevalence should be helpful in investigating possible environmental
influences on the development of MS.
DETAILS
Canada is known as having a prevalence rate of multiple sclerosis
that is among the highest in the world. Prevalence is the
number of known cases existing at one time within a particular
population (region, city or country). In MS, prevalence rates
are usually classified as high (greater than 30 cases per
100,000 population), medium (between five and 29 cases per
100,000) and low (less than five per 100,000).
Previous studies of MS prevalence in Canada
have ranged from 55 to 240 per 100,000. They have been generally
been confined to specific geographic areas and were not easily
comparable because of differences in methodology.
The researchers at the University of Calgary
(Dr. Cynthia Beck, Dr. Luanne Metz, and Dr. Scott Patten) and
Alberta Health and Wellness (Lawrence Svenson) reported the
results of their research in the October 2005 issue of the
journal Multiple Sclerosis (2005: 11). They used data
from the Statistics Canada 2001 Canadian Community Health Survey
(CCHS) to compare MS prevalence across regions at a single
time point, taking demographics into account. CCHS was a population-based
general health survey in which 131,535 Canadians were contacted
using a Statistics Canada developed sampling design. The data
provided information on MS (self reported), age, sex, immigration
status and ethnicity. Multiple sclerosis was among a number
of medical conditions on which data was collected in the survey.
For the MS prevalence analysis, the researchers used data from
survey respondents who were 18 and older (total 116,109). A
total of 332 respondents reported a diagnosis of MS.
According to the study researchers, the
overall weighted estimate of MS prevalence in Canada was 240
per 100,000. Prevalence was also reported by region: British
Columbia –
240 per 100,000; Prairie region – 340 per 100,000; Ontario
– 230 per 100,000; Quebec – 180 per 100,000; Atlantic
region – 350 per 100,000. Because of the small numbers
involved, prevalence was not broken out by province within
the Prairie and Atlantic regions.
The researchers conducted a number of modeling
analyses to adjust for age and sex and also tested the prevalence
findings against a smaller Canadian-born, non-aboriginal group
(total 96,219) within the original data set. These results
confirmed higher MS prevalence rates in the Atlantic and Prairie
regions.
According to Dr. William J. McIlroy, MS
Society National Medical Advisor, the study provides a new
way of looking at MS prevalence rates. Of particular note and
a new contribution to knowledge about MS are the variations
in MS rates across the country. These regional variations among
MS prevalence should be helpful in investigating possible environmental
influences on the development of MS.
Added Dr. Luanne Metz, one of the researchers,
“The study results support the existence of an environmental
factor or factors independent of latitude. Looking at differences
in the environment between these regions may help us uncover
additional factors that influence MS risk. In Canada, this
can be done as we are well organized, supported by the MS Society
of Canada and the population and socio-demographic influences
between regions varies relatively little but can be accounted
for.”
ASK MS Information System Code:
2.3.x
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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