Sarcoidosis is a multisystem disease that can affect all organ systems. Sarcoidosis severity rangesfrom asymptomatic patients with incidental radiographic abnormalities to patients with extensiveorgan impairment. Estimates of sarcoidosis incidence and prevalence vary because of differencesin study designs, time periods, geography, gender, age, and ethnicity. Sarcoidosis is associatedwith a favourable prognosis in the majority of patients, but can be fatal due to organ failure andend-stage sarcoidosis-related complications. The current literature on sarcoidosis-relatedmortality in the Nordic countries is limited. Sarcoidosis is primarily diagnosed in the working agepopulation hence, sarcoidosis-related working impairment may be associated with a personal andsocietal economic burden (indirect costs). Previous studies have found high healthcare costsrelated to sarcoidosis around the time of diagnosis and in cross-sectional studies. However,studies evaluating healthcare costs and indirect costs associated with sarcoidosis several yearsbefore and after diagnosis are limited. Depression and anxiety are frequently reported ascomorbidities in patients with sarcoidosis. However, literature reporting on the risk of developingdepression or anxiety after sarcoidosis is diagnosed is sparse.
The overall aim of this thesis was to evaluate the incidence and prevalence of sarcoidosis at anational level and the impact of sarcoidosis on important epidemiological aspects with a focus onsocioeconomic factors, mortality, and psychiatric comorbidity. The thesis includes four studiesbased on data from the Danish National Registries. In Studies II-IV, each case was matched withfour controls from the background population on age, gender, municipality, and civil status.
In Study I, we found an incidence of 14.5 per 100,000 per year. Incidence and prevalenceincreased from 2001 to 2015. In Study II, we evaluated the excess direct healthcare costs (hospitaladmissions, outpatient contacts, primary healthcare, and medication) and indirect costs (foregoneearnings, and public transfer income) in patients with sarcoidosis compared with matchedcontrols. Total excess costs (direct healthcare costs and indirect costs) were significantly higher incases compared with controls before and even more so after diagnosis. Inpatient admissions andforegone earnings from employment were the key drivers of excess costs.Mortality was higher in patients with sarcoidosis compared with matched controls during 18 yearsof follow-up (Study III). The highest mortality compared with the controls was seen in patients treated with systemic corticosteroids between three months before and three years afterdiagnosis.In Study IV, we followed patients with sarcoidosis and without anxiety or depression two yearsprior to diagnosis and their matched controls for 18 years after diagnosis. We found thatsarcoidosis cases had an increased risk of anxiety and/or depression in the 18-year study periodafter sarcoidosis diagnosis compared with the matched controls.
In conclusion, sarcoidosis imposes a substantial impact on patients´ lives in several ways. Theincidence and prevalence of sarcoidosis in Denmark are high. Sarcoidosis is associated with anincreased mortality and risk of anxiety and/or depression compared with matched controls. Thesocioeconomic burden associated with sarcoidosis is high, particularly at the time of diagnosis butalso several years before and before diagnosis. Overall, the thesis provides updated and novelknowledge on the epidemiology of sarcoidosis. Our findings can aid physicians when counsellingnewly diagnosed patients with sarcoidosis and hopefully inspire future research into some of thequestions that are raised based on our results.