OBJECTIVES : Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive form of fibrosing interstitial pneumonia. Some patients with IPF experience acute exacerbation (AE), with periods of relative stability followed by acute deteriorations in respiratory status. However, little is known about the epidemiology of AE. The objective of this study was to clarify the current status of AE among Japanese patients with IPF.

METHODS : We analyzed records of a Japanese claims database (April 2008-March 2019), covering over 20 million acute care hospital patients. IPF patients were identified using disease name, idiopathic pulmonary fibrosis. AE was defined as the prescription of steroid equivalent 500-1000 mg/day of methylprednisolone for three consecutive days. Proportion of patients who experienced AE were analyzed by calendar year, and incidence of AE from the first diagnosis was investigated.

RESULTS : A total of 9961 individuals were diagnosed as IPF, and age (mean±SD) at first diagnosis and the male ratio were 74.4 ± 9.3 years and 75%. The number of patients who experienced AE at least once was 1739 (17.4%). Of these 1739 patients, age (mean±SD) at first AE was 75.4 ± 8.8 years, and 79% were male. The proportion of patients with AE among IPF patients each year from 2013 to 2018 was 10, 9, 12, 10, 10, and 10%, respectively. The incidence of AE (events/person-year) each year from first to fifth year since the first diagnosis was 0.33, 0.13, 0.13, 0.12, and 0.14, respectively.

CONCLUSIONS : Nearly 17% of patients experienced AE at least once, and the proportion of patients with AE was stable for the last six years. The incidence was highest in the year of first diagnosis, but stable in later years. These results may suggest that patients were delivered to acute care hospitals once AE occurred. Further studies are needed to elucidate these findings.