Incidence and Mortality of Physician-Diagnosed Primary Sjögren Syndrome: Time Trends Over a 40-Year Period in a Population-Based US Cohort

Abstract

Objective: To estimate the incidence and mortality rates, and their evolution over time, of physician-diagnosed primary Sjögren syndrome (pSS) in residents of Olmsted County, Minnesota.

Patients and methods: Medical records of patients with a diagnosis or suspicion of SS in Olmsted County from January 1, 2006, through December 31, 2015, were reviewed to identify incident cases of pSS (defined by physician diagnosis). These cases were combined with those from a 1976 through 2005 incident cohort (n=111) from the same population. Incidence rates were age and sex adjusted to the 2010 US white population. Survival rates were compared with the expected rates in the population of Minnesota.

Results: With 61 incident cases of pSS diagnosed in Olmsted County from 2006 through 2015, the total cohort included 172 patients with incident pSS from 1976 through 2015. Of the 172 patients, 151 (88%) were women and 161 (94%) were white, with a mean ± SD age at diagnosis of 58.3±16.7 years. The average age- and sex-adjusted annual incidence for 2006 through 2015 was 5.9 per 100,000 population (95% CI, 4.4-7.4 per 100,000 population), and the overall incidence for the entire period was 5.8 per 100,000 (95% CI, 4.9-6.6 per 100,000). The incidence increased with calendar time over the 40-year period (P=.005). There was no difference in mortality in the pSS cohort compared with expected (standardized mortality ratio, 1.15; 95% CI, 0.86-1.50).

Conclusion: The average annual incidence of pSS in this population-based cohort was 5.8 per 100,000, with a progressive increase over the 40 years of the study. Overall survival of patients with pSS was not different from that of the general population.

Figure 1

Incidence over time (A), seasonality (B) and survival (C) in Olmsted County, Minnesota residents with incident primary Sjögren’s syndrome (SS) in 1976–2015 (n=172).