Incidence and prevalence of rheumatoid arthritis in Saskatchewan, Canada: 2001-2014.

Background: Rheumatoid arthritis (RA) is a chronic inflammatory and destructive arthritis. Understanding the incidence and prevalence of RA within the province facilitates appropriate health care resource planning.

Objective: To estimate the incidence/prevalence of RA over time for the overall provincial population, for specific age range categories, and for gender.

Methods: Saskatchewan Provincial Administrative Health Databases (2001-2014) were utilized as data sources. Two RA case-definitions were employed: 1) > three physician billing diagnoses, at least one of which was submitted by a specialist (rheumatologist, general internist or orthopedic surgeon) within 2 years; 2) > one hospitalization diagnosis (ICD-9-CM code-714, and ICD-10-CA code-M05). Data from these definitions were combined to identify incident and prevalent RA cases. Using this data, annual incidence and prevalence rates were calculated for the provincial population, specified age range categories and gender categories.

Results: The number of RA cases meeting the case definition increased from 3731 to 6223 over the study period. The incidence of RA disease demonstrated variation within the study period with age and sex adjusted incidence ranging from 33.6 (95% CI 29.9-37.6) per 100,000 to 73.1 (95% CI 67.6-79.0) per 100,000. The prevalence of RA increased over time from 482 (95% CI 466.7-497.7) per 100,000 in 2001-2002 to 683.4 (95% CI 666.6-700.6) per 100,000 in 2014-2015. Both incidence and prevalence rates rose with increasing age. Women were found to have higher incidence and prevalence rates compared to men.

Conclusion: In Saskatchewan, the overall prevalence of RA is rising while there has been variability in the incidence.