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Understanding low COPD exacerbation rates in Japan: a review and comparison with other countries

Authors Ishii T, Nishimura M, Akimoto A, James MH, Jones P

Received 10 February 2018

Accepted for publication 2 June 2018

Published 26 October 2018 Volume 2018:13 Pages 3459—3471

DOI https://doi.org/10.2147/COPD.S165187

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Colin Mak

Peer reviewer comments 4

Editor who approved publication: Dr Richard Russell


Takeo Ishii,1,2,* Masaharu Nishimura,3,* Asako Akimoto,1 Mark H James,4 Paul Jones4,5,*

1Respiratory Medical Affairs, Development and Medical Affairs, GSK K.K., Tokyo, Japan; 2Graduate School of Medicine, Nippon Medical School, Tokyo, Japan; 3Department of Respiratory Medicine, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan; 4Respiratory Franchise Medical, GSK House, Brentford, Middlesex, UK; 5Institute of Infection and Immunity, St George’s, University of London, London, UK

*These authors contributed equally to this work

Abstract: COPD is associated with significant morbidity and is one of the leading causes of death worldwide. Periods of exacerbation, the acute worsening of symptoms, are interspersed throughout the disease’s natural history and can result in increased treatment burden and hospitalization for patients with COPD. The frequency of exacerbations varies between countries, with both epidemiological studies and randomized controlled trials (RCTs) showing significant differences in observed prevalence rates. Differences in study design and the healthcare setting are likely to contribute to differences in exacerbation frequency, however the perceived rate of exacerbations in Japan is currently lower then the rest of the world. This review identified nine cohort studies and five RCTs that reported COPD annual exacerbation rates in Japan in the ranges of 0.1–2.1 and 0.33–1.79, respectively. The difference in exacerbation rate between studies appeared greater than the difference between Japan and Western countries, likely because of disparities between settings, design, and inclusion criteria. Of these, only one (Understanding the Long-Term Impacts of Tiotropium) had uniform inclusion criteria across different regions. This study found that the annual rate of exacerbation events per patient in Japan was 0.61, compared with 0.85 worldwide in the placebo groups. This review summarizes the published rates of COPD exacerbations in Japan and the rest of the world and explores the hypotheses as to why rates in Japan might be lower than other countries. These include access to medical care, variance in the associated morbidity profile, environmental factors, diagnostic crossover with related diseases, and differences in study design (including the underreporting of COPD exacerbations in Japan). Understanding the reasons why COPD exacerbation rates appear lower in Japan could help clinicians to recognize and modify treatment behaviors, which may lead to improved patient outcomes in all populations.

Keywords: COPD, exacerbation rate, asthma-COPD overlap, Japan

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