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. 2021 May;3(5):324-332.
doi: 10.1002/acr2.11251. Epub 2021 Apr 1.

Geographic Variation in the Prevalence of Rheumatoid Arthritis in Alberta, Canada

Xiaoxiao Liu  1 , Claire E H Barber  2 , Steven Katz  3 , Joanne Homik  3 , Stefania Bertazzon  1 , Alka B Patel  4 , Jill Robert  5 , Christopher Smith  6 , Dianne Mosher  1 , Deborah A Marshall  2
Affiliations

Geographic Variation in the Prevalence of Rheumatoid Arthritis in Alberta, Canada

Xiaoxiao Liu et al. ACR Open Rheumatol. 2021 May.

Abstract

Objectives: Timely access to rheumatologists remains a challenge in Alberta, a Canadian province with vast rural areas, whereas rheumatologists are primarily clustered in metro areas. To address the goal of timely and equitable access to rheumatoid arthritis (RA) care, health planners require information at the regional and local level to determine the RA prevalence and the associated health care needs.

Methods: Using Alberta Health administrative databases, we identified RA-prevalent cases (April 1, 2015-March 31, 2016) on the basis of a validated case definition. Age- and sex-standardized prevalence rates per 1000 population members and the standardized rates ratio (SRR) were calculated. We applied Global Moran's I and Gi* hotspot analysis using three different weight matrices to explore the geospatial pattern of RA prevalence in Alberta.

Results: Among 38 350 RA cases (68% female; n = 26 236), the prevalence rate was 11.81 cases per 1000 population members (95% confidence interval [CI] 11.80-11.81) after age and sex standardization. Approximately 60% of RA cases resided in metro (Calgary and Edmonton) and moderate metro areas. The highest rate was observed in rural areas (14.46; 95% CI 14.45-14.47; SRR 1.28), compared with the lowest in metro areas (10.69; 95% CI 10.68-10.69; SRR 0.82). The RA prevalence across local geographic areas ranged from 4.7 to 30.6 cases. The Global Moran's I index was 0.15 using three different matrices (z-score 3.96-4.24). We identified 10 hotspots in the south and north rural areas and 18 cold spots in metro and moderate metro Calgary.

Conclusion: The findings highlight notable rural-urban variation in RA prevalence in Alberta. Our findings can inform strategies aimed at reducing geographic disparities by targeting areas with high health care needs.

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Figures

Figure 1
Figure 1
Standard geographic areas in Alberta.
Figure 2
Figure 2
Distribution of rheumatoid arthritis (RA) rates at the local geographic area (LGA) level. The map displays the spatial distribution of RA rates based on the quartiles and includes information on quartiles, count of LGAs within this quartile, and the range of RA rates. Lighter color represents lower RA rates, and darker color represents higher RA rates. Upper outlier ranges between 1.5 times the interquartile range (IQR) above the third quartile (14.34) and the maximum (30.62).
Figure 3
Figure 3
Hotspots and cold spots of rheumatoid arthritis (RA) prevalence rates at the local geographic area (LGA) level by using three different spatial weight matrices. 8NN, eight nearest neighbors.
See this image and copyright information in PMC

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