Background/Purpose  High global prevalence rates of rheumatoid arthritis (RA) have been reported in First Nations (FN).  For our regional population of 1.2 million, health care is universally covered, and health services and diagnoses based on International Classification of Disease codes (ICD-9CM) are recorded in the Population Health Research Database (PHRD) from 1984. As a first step to addressing RA care in FN, we validated case definitions for RA for use with the PHRD and described the incidence, prevalence, and health care use for RA.

Methods Records from April 1, 1995 to March 31, 2010 were accessed.  FN people were identified using linkage with the Federal Indian Registry File (FIRF) which records all registered FN for the purposes of entitlement.  Identification was expanded to include non-status Indians otherwise eligible (Metis, Inuit). Residents who resided in the province for ≥2 years were identified as having RA if they had ≥5 physician visits or hospitalizations with (ICD)-9-CM/ICD-10 codes 714/M05, M06 recorded. Persons resident for <2 years were identified as having RA if they had ≥3 such claims. This definition was validated for the years 2000-2010 by linkage with the Arthritis Centre database (includes self-identified nonFN, FN, Metis; RA n=2281; nonRA n=7044; definition sensitivity 77.12, specificity 90.30 Youden statistic 67.42).  Crude and age standardized prevalence rates for FN and nonFN in 2000-2010 were determined.  Onset age, (age at first RA code), was compared in prevalent cases.  Using a 5 year run-in time to eliminate prevalent cases, incident RA cases were identified and compared between FN and non-FN using logistic regression and odds ratios with 95% CI reported.  Physician visits and hospitalizations were compared between FN and nonFN from 2000-2010.

Results While both crude and age standardized overall prevalence rates of RA increased from 2000-2010 (crude prevalence 0.34% to 0.65%), FN had higher rates than nonFN in each year. In 2009-2010, crude rates were 0.85% vs. 0.63% for FN vs. nonFN, while age adjusted rates were 1.0% vs. 0.4%; for a rate that was 2.48 times higher in FN than non-FN in 2009-2010 (95%CI 2.471-2.472; p<0.0001).  The age standardized annual incidence of RA decreased from 0.07% in 2000 to 0.02% in 2010. The overall incidence of RA was higher in FN than nonFN at most years with FN having 2.23 times higher incidence of RA in 2009-2010 (CI 2.22-2.23; p<0.0001).  RA onset age was earlier in FN than non-FN (41 vs. 55 years; p<0.001).  Despite greater physician visits (110 vs 99; p<0.0001) (all rates are per person over 10 years) and more hospitalizations (3.4 vs 1.9 p<0.0001), FN had fewer rheumatologist visits (6.9 vs 8.2 p<0.0001), non-rheumatology specialist visits (15 vs 23 p<0.0001) and surgeries (3.7 vs 5.3 p<0.0001) than non FN.

Conclusion While overall provincial RA incidence is decreasing, FN have more than twice the risk of developing RA, with a prevalence of 1% in 2009-2010, as well as an onset age 10 years earlier than the general population.  When combined with generally more severe disease in FN and fewer rheumatology visits this demonstrates a significant care gap highlighting the need to optimize rheumatology care delivery to this population, particularly in view of the rapid growth of this population.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/first-nations-persons-have-an-increased-risk-of-developing-rheumatoid-arthritis-with-an-early-onset-age-but-are-seen-less-frequently-by-rheumatologists-a-population-based-study/