Clinical characteristics of Japanese patients with chronic obstructive pulmonary disease (COPD) with comorbid interstitial lung abnormalities: A cross-sectional study.

Smoking-related interstitial lung abnormalities are different from specific forms of fibrosing lung disease which might be associated with poor prognoses. Chronic obstructive pulmonary disease with comorbid interstitial lung abnormalities and that with pulmonary fibrosis are considered different diseases; however, they could share a common spectrum. We aimed to evaluate the clinical characteristics of Japanese patients with chronic obstructive pulmonary disease and comorbid interstitial lung abnormalities. In this prospective observational study, we analyzed data from the Ishinomaki COPD Network Registry. We evaluated the clinical characteristics of patients with chronic obstructive pulmonary disease with and without comorbid interstitial lung abnormalities by comparing the annualized rate of chronic obstructive pulmonary disease exacerbations per patient during the observational period. Among 463 patients with chronic obstructive pulmonary disease, 30 (6.5%) developed new interstitial lung abnormalities during the observational period. After 1-to-3 propensity score matching, we found that the annualized rate of chronic obstructive pulmonary disease exacerbations per patient during the observational period was 0.06 and 0.23 per year in the interstitial lung abnormality and control groups, respectively (P = 0.043). Our findings indicate slow progression of interstitial lung abnormality lesions in patients with pre-existing chronic obstructive pulmonary disease. Further, interstitial lung abnormality development did not significantly influence on chronic obstructive pulmonary disease exacerbation. We speculate that post-chronic obstructive pulmonary disease interstitial lung abnormalities might involve smoking-related interstitial fibrosis, which is different from specific forms of fibrosing lung disease associated with poor prognoses.