The prevalence and disease burden of severe eosinophilic asthma in Japan

Abstract

Background: There are limited data on the prevalence and burden of severe eosinophilic asthma (SEA) both in Japan and globally. This study aimed to assess the prevalence and burden of SEA in Japan. Methods: This study was a retrospective, observational cohort analysis using health records or health insurance claims from patients with severe asthma treated at Kyoto University Hospital. The primary outcome was the prevalence of SEA, defined as a baseline blood eosinophil count ≥300 cells/μL. Secondary outcomes included frequency and risk factors of asthma exacerbations, and asthma-related healthcare resource utilization and costs. Results: Overall, 217 patients with severe asthma were included; 160 (74%) had eosinophil assessments. Of these, 97cases (61%), 54cases (34%), and 33cases (21%) had a blood eosinophil count ≥150, ≥300, and ≥500 cells/μL, respectively. Proportion of SEA was 34%. Blood eosinophil count was not associated with a significantly increased frequency of exacerbations. In the eosinophilic group, lower % forced expiratory volume in 1 second and higher fractional exhaled nitric oxide were predictive risk factors, while the existence of exacerbation history was a predictive risk factor for asthma exacerbations in the non-eosinophilic group. Severe asthma management cost was estimated as ¥357,958/patient-year, and asthma exacerbations as ¥26,124/patient-year. Conclusions: Approximately, one-third of patients with severe asthma in Japan have SEA. While risk factors for exacerbations differed between SEA and severe non-eosinophilic asthma, both subgroups were associated with substantial disease and economic burden. From subgroup analysis, blood eosinophil counts could be an important consideration in severe asthma management.

Keywords:

• Epidemiology
• healthcare resource utilization
• asthma management cost
• predictive risk factor
• exacerbation

Acknowledgement

Editorial support (in the form of writing assistance, including development of the initial draft based on author direction, assembling tables and figures, collating author comments, and grammatical editing and referencing) was provided by Chris Tan, PhD, at Fishawack Indicia Ltd, UK, and was funded by GSK.

Disclosure statements

KS, TOh, AM, AK, and TKa are employees of GlaxoSmithKline (GSK); KS, AK, and TKa hold stock/shares in GSK; HM received personal fees from GSK; NK, II, YI, TKu, HM, MM, TN, TOg, KO, SK and HS received research funding for the current study from GSK Japan.

Additional information

Funding

This study was funded by GSK (205547/HO-15-15492). GSK employees contributed to the study design, analysis, and interpretation of data, the writing of the manuscript and the approval of the final version to be submitted. The decision to submit for publication was that of the authors alone. The sponsor did not place any restrictions on access to the data or on the statements made in the manuscript. The authors had full access to all the data in the study and had final responsibility to submit for publication.