Regional variation of multiple sclerosis prevalence in Canada

OBJECTIVE: To describe the regional distribution of multiple sclerosis (MS) prevalence in Canada, controlling for age and sex. METHODS: This study used data from the Canadian Community Health Survey, a large general health survey (n = 131,535) conducted in 2000/2001. Subjects aged 18 and over were included in the current analysis (n = 116,109). The presence of MS was determined by self-report. Prevalence was computed in five regions (Atlantic, Quebec, Ontario, Prairies and British Columbia). Logistic regression was used to compare regions and examine for confounding/interaction by age and sex. RESULTS: The overall Canadian MS prevalence was 240 per 100000 (95%CI: 210 280). Prevalence ranged from 180 (95%CI: 90-260) in Quebec to 350 (95%CI: 230-470) in Atlantic Canada. Logistic regression revealed no statistical difference between the odds of MS in Quebec, Ontario and British Columbia adjusted for age and sex. The adjusted odds of MS in the Prairies and Atlantic regions were significantly higher than in the other regions combined, with odds ratios of 1.7 (95%CI: 1.1-2.4, P <0.01) and 1.6 (95%CI: 1.1-2.4, P <0.05) respectively. Sensitivity analysis demonstrated similar prevalence in the nonaboriginal/nonimmigrant group (n = 96219). CONCLUSION: Results suggest that Canadian MS prevalence differs by region. If validated, these regional differences may facilitate investigation of environmental influences.