Epidemiology of systemic sclerosis in Quebec, Canada: a population-based study

Systemic sclerosis (SSc) is a systemic life-threatening autoimmune rheumatic disease. We aimed to assess the incidence, prevalence, mortality and spatiotemporal trends of SSc in Quebec, Canada with stratification by sex and age.

SSc cases were identified from Quebec populational databases from 1989 to 2019. Negative Binomial (NB) Generalized Linear Models were used for age-standardized incidence rates (ASIR) analyses and NB random walk for prevalence and mortality. A Poisson Besag-York-Mollié regression model was used for spatial analysis.

8180 incident SSc cases were identified between 1996 and 2019 with an average age of 57.3 ± 16.3 years. The overall ASIR was 4.14/100,000 person-years (95%, Confidence Interval (CI) 4.05-4.24) with a 4:1 female predominance. ASIR increased steadily over time with an Average Annual Percent Change (AAPC) of 3.94% (95% CI 3.49-4.38). While the highest incidence rates were in those aged 60-79 years old among females and >80 years old among males, the highest AAPC (∼10%) was seen in children. Standarized incidence ratios varied geographically between 0.52 to 1.64. The average prevalence was 28.96/100,000 persons (95% CI 28.72-29.20). The Standardized Mortality Ratio (SMR) decreased from 4.18 (95% CI 3.64-4.76) in 1996 to 2.69 (95% CI 2.42-2.98) in 2019. Females had a greater SMR until 2007 and males thereafter. The highest SMR was in children and young adults [31.2 (95% CI 8.39-79.82) in the 0-19-year age group].

We showed an increasing trend in SSc incidence and prevalence and a decline in SMR over a 25-year period in Quebec. An uneven geographic distribution of SSc incidence was demonstrated.

National Scleroderma Foundation, Canadian Dermatology Foundation/Canadian Institutes of Health Research.