Quebec Rheumatoid Arthritis Study Finds Urban-rural Prevalence Deviance

Quebec Rheumatoid Arthritis Study Finds Urban-rural Prevalence Deviance

shutterstock_181676285Rheumatoid arthritis (RA), one of the two most common (with osteoarthritis) types among than 100 arthritic inflammatory joint disorders, is a chronic, systemic, autoimmune, inflammatory disease in which the body’s immune system dysfunctionally attacks primarily the lining of skeletal joints, but can also damage internal organs such as the eyes, lungs or heart. The abnormal immune response associated with RA causes swelling, pain, inflammation, and joint destruction. As the disease progresses, increasingly more joints become affected on both sides of the body often in a symmetrical or “mirror” pattern; ergo: if right hand joints are swollen, there’s strong likelihood that joints in the left hand will also swollen.

There can be a wide variance in RA symptoms from person to person, with some having only a few joints involved or mild inflammation, while with others many joints will be involved and/or inflammation may be severe. RA symptoms tend to wax and wane from intervals when the joints will feel relatively good to other times (often for no apparent reason) they will become stiff, sore and swollen. Pain, stiffness, swelling and/or deformity of the joints caused by the inflammation can significantly reduce quality of life for RA sufferers.

Approximately 300,000 Canadians (about one out of every 100) and 1.5 million Americans have rheumatoid arthritis, which can manifest at any age, but most often appears between the ages of 25 and 60, and affects women three times more often than men — in whom it more often occurs later in life.

Statistics Canada metrics based on the Canadian Community Health Survey for 2012 say 15.4% (4.4 million) of Canadians aged 15 and older reported that they had been professionally diagnosed with some type of arthritis excluding fibromyalgia, with overall incidence having remained roughly static since 2007, and 12.1% of males and around 19% of females reporting the condition in 2012.

However Quebec was the only province in the ten in which residents reported a rate of arthritis (10.8%) lower than the national average (15.4%), which is less than half the rates in the worst-affected provinces of Newfoundland and Labrador (23.6%), and Nova Scotia (22.7%) — a seemingly radical deviation.

Statistics Canada does note that in the 2011 Canadian Community Health Survey French-language questionnaire, the word “arthrose” was added to the arthritis question, since patients tend to associate the word “arthrite” with rheumatoid arthritis and “arthrose” with degenerative arthritis (osteoarthritis). However, the word “arthrose” was omitted from the question in 2012 with as a result, arthritis estimates for the province of Quebec and subsequently the national Canada level affected, which may account for some of the statistical deviance. However, even back in 2008, Quebec residents were less likely than Canadians in general to report arthritis.

A new research article published 19 December 2014 by BioMed Central in the Open Access journal BMC Research Notes examines the RA incidence rate in Quebec using administrative health data, physician billing and hospitalization data from 1992-2008 compared across regions.

Entitled “Rheumatoid arthritis prevalence in Quebec,” (BMC Research Notes 2014, 7:937 doi:10.1186/1756-0500-7-937), the article is coauthored by Sasha Bernatsky MD, PhD and Christian Pineau MD, both associate professors and members of the Medicine Research Institute at McGill University Health Centre in Montreal; Alaa Dekis, MD; Marie Hudson, MD, an assistant professor in the Department of Medicine at McGill and physician-scientist at Montreal’s Jewish General Hospital;, Gilles Boire, M. D., M. Sc, a rheumatologist and full professor in the Faculty of Medicine at the University of Sherbrooke; Paul Fortin MPH, MD, FRCPC, an Affiliate Scientist at Toronto Western Research Institute (TWRI); Louis Bessette Director of the Rheumatology Program at Laval University and a rheumatologist at the Centre Hospitalier de l’Université Laval (CHUL); Sonia Jean Ph D of the Laval University Department of Medicine; Anne-Laure Chetaille of the University of Manitoba; Patrick Belisle, Louise Bergeron, patient advocate and president of the Canadian Arthritis Patients’ Alliance (CAPA); Debbie Feldman pht., Ph.D. of the Direction de la Santé Publique and École de réadaptation, Université de Montréal and Lawrence Joseph, a Professor in the Department of Epidemiology and Biostatistics at McGill University.

Dr. Bernatsky’s research at McGill focuses on outcomes of rheumatic diseases, including morbidity, mortality, and the economic impact of conditions such as rheumatoid arthritis, juvenile idiopathic arthritis, systemic lupus erythematosus (SLE) and fibromyalgia. Dr. Boire’s research focus is on developing predictive biomarkers of clinical outcomes in patients with recent-onset inflammatory polyarthritis, and early diagnosis of inflammatory arthritis essential for treatment.

Using three case definitions: 1) billing diagnoses, submitted by any physician; 2) diagnosis, by a rheumatologist; and 3) hospitalization diagnosis, the researchers combined data across these three defined categories, employing Bayesian hierarchical latent class models to derive an estimate of RA prevalence. The imperfect sensitivity and specificity of the data were adjusted for, and urban versus rural regions compared.

The coauthors report that using the above outlined case definitions and no adjustments for error, they defined 75,760 cases, which calculates to overall RA prevalence of 9.9 per thousand residents. After applying adjustment for the study’s case definition algorithms’ imperfect sensitivity and specificity, the researchers estimated RA prevalence in Quebec at 5.6 per 1000 for females and 4.1 per 1000 for males, with adjusted RA prevalence estimates for older females highest among demographic groups (9.9 cases per 1,000), and results were similar cross-referenced between rural and urban regions. Among younger persons of both genders, and in older males, RA prevalence estimates tracked lower in rural areas than among urban dwellers.

The researchers calculate that with no adjustment for errors inherent in administrative databases, a finding that RA prevalence in Quebec is approximately 1%, with adjusted estimates roughly half that, and that lower RA prevalence in rural areas recorded across most demographic groups, may indicate either actual regional variations in RA risk, or under-reporting of cases in rural Quebec, suggesting that more research would be necessary to reach a more definitive conclusion.

BMC Research Notes
The Arthritis Society
The Arthritis Foundation

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