Change in the incidence of Behcet’s disease (BD) from long-term population‐based data are scarce, although a possible decline has been reported. The objectives were to investigate the incidence, survival, and mortality of BD patients from 2004 to 2017 in South Korea.

We analyzed a registry of rare intractable diseases and a claims database from the Health Insurance and Review Agency with information on BD patients between 2004 and 2017 using uniform diagnostic criteria. The study period was divided into three groups: 2004–2006, 2007–2010, and 2011‐2017. The annual incidence of BD decreased from 8.15 per 100,000 in 2004 to 1.51 in 2017, an 81.5% decrease. The annual percentage change was 6.32% for females and 6.15% for males. The decrease in BD incidence was more remarkable for women and middle‐aged people. The 3‐year survival rate of BD patients during the 2011‐2017 period was lower than those of the BD patients in 2004‐2006 and 2007‐2010, although there was no statistical difference. The standardized mortality rates increased significantly in the 2011‐2017 period compared to the first two periods.

BD incidence decreased from 2004 to 2017 in South Korea. This decline in incidence might be attributable to changes in environmental factors, including reducing the burden of infectious diseases in the past decades and improving oral health during childhood. The unprecedented decline in the incidence of BD in South Korea without significant changes in the genetic background suggests that environmental factors are essential to BD development.