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

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.

<p>Unique Mortality Profile in Japanese Patients with COPD: An Analysis from the Hokkaido COPD Cohort Study</p>

“…However, it must be noted that the mean age of Japanese patients with COPD requited for most clinical studies, including some worldwide clinical trials, was also around 70 years old, which was definitely older than around 65 years old reported from other countries. [1][2][3] This fact suggests that the subjects in this study reflect well the reality of Japanese patients with COPD.…”

“…However, the extreme male predominance in Japanese patients with COPD has been reported in several clinical studies. [1][2][3] Third, we did not collect exacerbation data for the last 5 years, and this might have affected the mortality profile. Lastly, there may be a survival bias in the recruitment of subjects in this study.…”

“…Japanese patients with chronic obstructive pulmonary disease (COPD) are generally older, thinner, and experience fewer exacerbations than do their Western counterparts, as shown by a literature search 1 as well as direct comparisons made among patients with COPD recruited using the same inclusion criteria in various worldwide clinical trials. 2,3 Thus, the mortality profile of Japanese patients might be unique and different from that reported elsewhere, particularly from the Western society.…”

Per cent low attenuation volume and fractal dimension of low attenuation clusters on CT predict different long-term outcomes in COPD

“…This strategy increases the validity of our study. Second, the subjects in both cohorts were predominantly male, which reflects the sex distribution of patients with COPD in Japan 39. Given the sex-related difference in severity of emphysema,40 it is unclear whether our findings can be generalised to female patients with COPD.…”

<p>Simple standard equation for daily step count in Japanese patients with chronic obstructive pulmonary disease</p>

“…The step count of Japanese patients with COPD might be relatively higher compared to other countries. Furthermore, Japanese patients with COPD were reported to be relatively older,35 milder stage,36–38 and have fewer exacerbations36,39 than those in other countries. As PA is influenced by several factors including regional customs, economic condition and environment, the recommended step count might ideally be set separately in each country.…”