Epidemiology of non-cystic fibrosis bronchiectasis at a single center in Japan: a retrospective cohort study

Background: The characteristics of non-cystic fibrosis bronchiectasis (NCBE) in Asia, including Japan, remain largely unknown. We aimed to provide insights into the clinical characteristics and treatment outcomes of NCBE, especially regarding nontuberculous mycobacteria (NTM) infection, and establish a basis for comparison with global datasets. In addition, long-term macrolide antibiotic use in patients with NCBE and a history of exacerbations is established, but the effects in patients without exacerbations remain unclear. Methods: In this single-center, retrospective study, the medical records of patients who satisfied the NCBE criteria between 1 January 2012 and 31 August 2023 were reviewed. Severe exacerbations and mortality during the observation period were recorded. Baseline characteristics, prognostic factors, and overall survival of patients with and without non-NTM infection were evaluated; effects of long-term macrolide antibiotic use in patients without severe exacerbations were estimated using inverse probability weighting (IPW). Results: In 1044 patients with bronchiectasis, severe exacerbation rates were 22·32%, with mortality rates of 3·16% at 3 years. Notably, the high prevalence of NTM infection (n=458, 43·87%) in this cohort was distinctive. Compared with the NTM group, the non-NTM group had a higher proportion of elevated inflammatory markers, with significant differences in C-reactive protein levels (p=0·0023) and blood neutrophil counts (p<0·001). Pseudomonas aeruginosa was more frequently identified as having colonization and was associated with severe exacerbations (p<0·001) in the non-NTM group. NTM infection was not associated with mortality (p=0·4621, hazard ratio=0·79). Among patients with non-NTM infection and without a history of exacerbation in the past 2 years, 34·3% received long-term macrolide antibiotics that did not invariably reduce severe exacerbations (P=0·3801, IPW P=0·7222). Conclusions: This study highlights NCBE epidemiology in Japan, advising caution in the casual use of macrolides for mild cases. Clinical Trial Registration: UMIN Clinical Trials Registry Number: UMIN000054726 (Registered on 21 June 2024)