Prevalence of idiopathic pulmonary fibrosis in Japan based on a claims database analysis

Abstract

Background: Idiopathic pulmonary fibrosis (IPF) is a cryptogenic chronic interstitial pneumonia with progressive fibrosis and a poor prognosis. A substantial number of epidemiological studies have been conducted in Europe and the United States (US). In contrast, in Japan, only one study reported the prevalence of IPF (10.0 per 100,000 population) using clinical data (2003-2007) from one prefecture; thus, the nationwide prevalence of IPF remains unknown. This study aimed to estimate the nationwide prevalence of IPF in Japan using a nationwide claims database.

Methods: We extracted data from a Japanese claims database provided by Medical Data Vision (MDV database, April 2008-March 2019) containing data from approximately 28 million patients from 385 acute-care hospitals. Patients with IPF (those diagnosed with IPF at least once) from April 2017 to March 2018 were identified in the MDV database. The number of patients in the MDV database was extrapolated nationwide using the fourth NDB Open Data (April 2017-March 2018), and the prevalence was estimated using demographic data as denominators. The prevalence in the US, considering the same definition of IPF, was also calculated and compared with that in Japan.

Result: The number of patients with IPF in the MDV database was 4278. The estimated nationwide number of patients in Japan was estimated to be 34,040 (mean age: 73 years, percentage of men: 73%), and the prevalence was 27 per 100,000 population. In comparison with that in the US, the prevalence was similar in men and relatively lower in women until the age of 75-79 years, and it was notably lower in both sexes aged ≥ 80 years.

Conclusions: We report the nationwide IPF prevalence in Japan using data from claims databases for the first time. The prevalence estimated in this study was higher than that reported in a previous study. The difference might be due to differences in study settings and definitions of IPF. Further research should be performed to determine the prevalence more accurately and compare it with those in other countries.

Keywords: Claims data; Epidemiology; Idiopathic pulmonary fibrosis; Japan; Prevalence.

Fig. 1

Diagram of the prevalence estimation method. ^aThe other databases includes the database provided by JMDC, IBM MarketScan Commercial Database, and Medicare 5% sample data. MDV database consists of claims data from acute care hospitals, and does not contain population data. NDB Open Data is a publicly available summary spreadsheet from National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB), which contains almost all health insurance claims data. In the NDB Open Data, 100 of the most prescribed drugs for each therapeutic category, including pirfenidone, in a one-year period from April are summarized for each age and sex group. IPF Idiopathic pulmonary fibrosis; MDV Medical Data Vision

Fig. 2

Age- and sex-specific prevalence of idiopathic pulmonary fibrosis in Japan and the US in a men and b women. The prevalence was estimated based on the Medical Data Vision Co., Ltd database, fourth NDB Open Data [15], and demographic data [16] (April 2017–March 2018) for Japan and the IBM MarketScan Commercial Database (January–December 2017) for aged < 65 years and Medicare 5% sample data (January–December 2018) for aged ≥ 65 years for the US. Dotted lines indicate 95% confidence intervals

Fig. 3

Percentage of patients with idiopathic pulmonary fibrosis with examinations for those aged ≥ 65 years in Japan and the US in a men and b women. The percentage was calculated by dividing the number of patients who underwent examinations at least once during the 2018 calendar year by the number of patients diagnosed with idiopathic pulmonary fibrosis in 2018. Examinations included high-resolution computerized tomography, bronchoalveolar lavage, transbronchial lung biopsy, or surgical lung biopsy