Background/Purpose: Estimates of prevalence of primary Sjögren’s syndrome (pSS) are conflicting, ranging from 1 to more than 8 cases per 10,000 according to different population-based studies. No prevalence data for the U.S. population are available so far. The objective of this work was to estimate the 2015 point prevalence of primary Sjögren’s syndrome (pSS) in a population-based study performed in the United States.

Methods: This study was performed in a well-defined U.S. population which counted approximately 157,000 inhabitants as of January 1, 2015. Individual medical record review of all cases was previously performed to obtain the total number of incident pSS cases by physician diagnosis from 1976-2005 (1). Prevalence estimates for this study are based on the same source population, assuming that the disease was not associated with excess mortality, as previously shown, and that migration in or out of the census population was independent of disease status. Annual incidence rates were stable for the 1976-2000 period but increased over time between 2000 and 2005 (figure). Therefore, different prevalence estimates were computed according to stable or increasing incidence rate scenarios between 2006 and 2015. Prevalence was age- and sex-adjusted to US white 2010 population.

Results: A total of 105 pSS cases were diagnosed in this population between 1976 and 2005, with annual incidence rates varying between 2 and 8 cases/100,000/year (figure). Using several scenarios for incidence estimates between 2006 and 2015 based upon previous data (table), the projected 2015 prevalence in this population ranged between 9.5 and 36.9 per 10,000. The prevalence was estimated between 0.6 and 3.1 per 10,000 in males and between 18.0 and 69.1 per 10,000 in females.

Conclusion: Our estimated prevalence range is substantially higher than previously published population-based pSS prevalence studies conducted in other geographical area. This finding could reflect important variations of physician diagnosis during the 40-year period during which incidence rates were previously assessed in this population. New epidemiological population-based studies are warranted, using validated and consensual classification criteria for case ascertainment. Reference: (1) Nannini C et al, BMJ Open. 2013 Nov 25;3(11):e003569.