A multi-country cohort study evaluating the prevalence, risk factors, lung function and clinical outcomes of chronic bronchitis in low- and middle-income countries

BACKGROUND: Chronic bronchitis affects up to 40% of individuals with COPD, and may serve as an early predictor of the disease and development of COPD. We investigated the prevalence, risk factors and clinical outcomes associated with chronic bronchitis in three low- and middle-income countries (LMICs). METHODS: We conducted a population-based study of adults aged ≥40 years in Bhaktapur (Nepal), Lima (Peru) and Nakaseke (Uganda). Chronic bronchitis was defined as a productive cough several days per week in the past 4 weeks. Multivariable log-binomial regression identified risk factors and outcomes associated with chronic bronchitis. RESULTS: Among 9664 participants (mean age 56.2 years, 49.0% male, 33.1% ever-smokers), chronic bronchitis prevalence was 9.7%, with 31.5% of those also having COPD. Significant risk factors included older age (adjusted relative risk 1.54, 95% CI 1.40-1.70; per 19.8 years), male sex (1.18, 95% CI 1.05-1.34), prior tuberculosis (1.45, 95% CI 1.14-1.83), prior asthma diagnosis (2.11, 95% CI 1.84-2.42), pack-years of tobacco use (1.16, 95% CI 1.14-1.18; per 10 pack-years), family history of chronic respiratory disease (1.69, 95% CI 1.50-1.91), second-hand smoke exposure (1.45, 95% CI 1.28-1.64), lower socioeconomic status quartile (1.22, 95% CI 1.07-1.39) and indoor biomass exposure (1.45, 95% CI 1.13-1.86). Participants with chronic bronchitis experienced more breathlessness, worse respiratory health (higher St George's Respiratory Questionnaire scores) and higher hospitalisation rates (all p<0.001). CONCLUSIONS: Chronic bronchitis is common in LMIC settings and is associated with multiple modifiable risk factors, including second-hand smoke, biomass exposure and prior respiratory disease. Addressing these factors may reduce disease burden and improve quality of life.