The 5-year survival rate of Japanese patients (73%)
in the present study was a little higher than previously
reported, because the 5-year mortality rate of
patients with COPD typically varies from 40 to 70%
depending on disease severity.21 The morbidity and
mortality of patients with COPD can vary with the
country or region, and our results are consistent with
a past report indicating that COPD mortality was
lowest in Japan among 31 developed countries.22
However, the number of cases analyzed in the
present study was less than in other studies,17 and a
more detailed statistical analysis of a larger number
of cases may be required to confirm results.