Incidence and prevalence of multiple sclerosis in Saskatoon, Saskatchewan

Walter J. Hader, MD, FRCPC and Irene M.L. Yee, MSc

From the Department of Physical Medicine and Rehabilitation (W.J.H.), University of Saskatchewan, Saskatoon, Saskatchewan, Canada; and the Faculty of Medicine (I.M.L.Y.), Department of Medical Genetics, University of British Columbia, Vancouver, Canada.

Objective:  

To determine the incidence of multiple sclerosis(MS) in a longitudinal surveillance over 35 years and to estimatethe prevalence rate in Saskatoon, Saskatchewan, on January 1,2005.

Methods:

A population-based registry was established in 1969,and identification of cases continued to 2005, from medicalrecords, physicians, neurologists, community, and provincialresources.  A modified classification of Allison and Millar andthe Schumacher diagnostic criteria were originally applied,and patients with definite and probable MS were included. Therates were age- and sex-adjusted to the US, European, and world2000 populations.

Results:

From 1970 to 2004, there were

­       558 incidence casesidentified,

­       402 women and

­       156 men,

for a sex ratio of 2.6:1The average annual incidence rate was 9.5 in 100,000 (95% CI8.8 to 10.4) and was stable over the three decades. The innaterisk or residence at onset rate was 197 in 100,000 (95% CI 170to 226). The crude prevalence rate for the living 587 caseson January 1, 2005, was 298.3 in 100,000 (95% CI 274.7 to 323.6).

Conclusions:

The incidence and prevalence rates adjusted tothe standardized populations were statistically higher thanthe longitudinal European studies and similar to North Americanstudies.  Our incidence study confirms the high risk of multiplesclerosis (MS) in Saskatoon, and these rates seem to be stableover the past 35 years. The high crude prevalence rate resultsfrom an accumulation of incidence and non-resident cases overtime. Long-term follow-up studies and comparison with standardize dpopulations are recommended to estimate reliable incidence andthe true risk of MS in the world.

© 2007 American Academy of Neurology