Bronchiectasis prevalence, incidence, and exacerbation rates among insured adults in the U.S.: a descriptive analysis

RATIONALE: Contemporary population-representative data on bronchiectasis epidemiology in the United States remain limited. Existing exacerbation estimates are derived primarily from referral registries that overrepresent severe disease under subspecialty care, while incidence and prevalence calculations are largely based on outdated single-payer data, limiting generalizability. OBJECTIVES: To estimate non-cystic fibrosis bronchiectasis prevalence and incidence among insured U.S. adults during 2016-2024, characterize exacerbation rates and their composition, and identify baseline factors associated with subsequent exacerbations. METHODS: We assembled a retrospective cohort of adults with bronchiectasis using MarketScan Commercial, Medicare Supplemental, and Medicaid databases. Cases required two or more bronchiectasis diagnostic claims separated by more than 30 days, excluding individuals with cystic fibrosis, human immunodeficiency virus infection, or organ transplantation. The observation time zero was the second qualifying claim. Quasi-Poisson models were used to estimate annual prevalence, incidence, and exacerbation rates during observable enrollment periods. Annual percent changes quantified temporal trends. A negative binomial model estimated associations between baseline characteristics and post-diagnosis exacerbation rates. RESULTS: We identified 80,749 cases (64.6% female; mean age 65.9 years) and estimated prevalence and incidence of 105.3 and 32.1 per 100,000, respectively, in the combined Commercial-Medicare sample, and 66.1 and 19.0, respectively, in Medicaid. Prevalence increased steadily across payers, whereas incidence remained stable. The overall exacerbation rate was 0.88 events per person-year, declining by approximately 5% annually, with a reduction during the early pandemic period followed by a return to pre-pandemic trajectories by 2024. Outpatient events accounted for nearly 87% of exacerbations in the Commercial-Medicare sample and 65% in Medicaid. Calendar trends were attenuated by 12.3% after adjustment for follow-up. Frequent-exacerbator phenotype at cohort entry was the most strongly associated with higher subsequent exacerbation rates (adjusted rate ratio 1.96), followed by chronic airway infection and underlying respiratory conditions. Greater pulmonologist engagement at baseline was associated with lower exacerbation rates thereafter. CONCLUSIONS: Observed prevalence-incidence widening gap suggests case accumulation over time and survival among continuously enrolled beneficiaries. Exacerbation burden was concentrated among individuals with prior exacerbations, chronic airway infection, and respiratory comorbidity, while exacerbation rates decreased over time across payers and subgroups, in part reflecting changes in cohort composition.