Prevalence and Incidence of Rheumatoid Arthritis in Canadian First Nations and Non–First Nations People: A Population-Based Study

The aim of this study was to determine the prevalence, incidence, and onset age at rheumatoid arthritis (RA) diagnosis in First Nations (FN) and non-FN populations in Manitoba, Canada. METHODS: Population-based administrative health records from April 1, 1995, to March 31, 2010, were accessed for all Manitobans. The FN population was identified using the Federal Indian Registry File. Crude and adjusted RA prevalence and incidence rates (adjusted for age, sex, health region of residence) were compared using Poisson regression and reported as relative rates (RRs) with 95% confidence intervals (CIs). Mean (CI) diagnosis age and physician visits were compared with Student t tests. RESULTS: Rheumatoid arthritis crude prevalence increased between 2000 and 2010 to 0.65%; adjusted RA prevalence in females was 1.0% and in males was 0.53%. The 2009/2010 adjusted RA prevalence was higher in FN than non-FN (RR, 2.55; CI, 2.08–3.12) particularly for ages 29 to 48 years (RR, 4.52; CI, 2.71–7.56). Between 2000 and 2010, crude RA incidence decreased from 46.7/100,000 to 13.4/100,000. Adjusted RA incidence remained higher in FN than non-FN (2000–2010 RR, 2.1; CI, 1.7–2.6; p < 0.0001) particularly for ages 29 to 48 years (RR, 4.6; CI, 2.8–7.4; p < 0.0001). The FN population was younger at diagnosis than the non-FN population (mean age, 39.6 years [CI, 38.3–40.8 years] vs. 53.3 years [CI, 52.7–53.9 years]; p < 0.0001). The FN population had more physician visits but fewer rheumatology visits than the non-FN population. CONCLUSIONS: Rheumatoid arthritis prevalence is increasing, and RA incidence is decreasing in Manitoba. The FN population has a greater prevalence and incidence of RA and is younger at diagnosis than the non-FN population. When combined with fewer rheumatology visits, this significant care gap highlights the need to optimize rheumatology care delivery to the FN population.