Sarcoidosis: A nationwide registry-based study of incidence, prevalence and diagnostic work-up

Introduction: The primary objective was to evaluate the prevalence and incidence of sarcoidosis, and secondly, to evaluate differences in incidence by age at diagnosis, gender, region, calendar year and treatment and to evaluate sarcoidosis-related diagnostic work-up. Methods: Patients diagnosed with sarcoidosis from 2001 to 2015 and information on diagnostic procedures three months before and after initial diagnosis were identified in the Danish National Patient Register. Incidence proportion and prevalence proportion were calculated using the total population count of Danish citizens. Results: We identified 8545 sarcoidosis cases. Mean age was 46.0 +/- 15.0 years, male gender was overrepresented (56.2%) and systemic corticosteroid was initiated in 46% of cases. The prevalence was 77 per 100,000 citizens in 2015. From 2001 to 2015, the incidence varied from 11.3 to 14.8 per 100,000 per year. The age-associated incidence peaked at 30-39 years in both men (23.6 per 100,000 per year) and women (15.0 per 100,000 per year). Incidence varied from 10.4 to 15.7 per 100,000 per year among regions. In particular, the share of bronchoscopies and chest-computed tomography were high in the region with the highest incidence and low in the region with the lowest incidence. Invasive procedures were more frequently performed in patients treated with systemic corticostemid. Conclusion: We find an increasing incidence and prevalence of sarcoidosis, with a peak incidence for both men and women between 30 and 39 years of age. The share of procedures performed seems to correlate well with incidence and disease severity.