Urbanization and daily exposure to biomass fuel smoke both contribute to chronic bronchitis risk in a population with low prevalence of daily tobacco smoking

Objective: Risk factors beyond tobacco smoking associated with chronic bronchitis are not well understood. We sought to describe the prevalence and risk factors of chronic bronchitis across four distinct settings in Peru with overall low prevalence of tobacco smoking yet varying degrees of urbanization, daily exposure to biomass fuel smoke and living at high altitude. Methods: We analyzed data of 2,947 participants from rural and urban Puno, Lima and Tumbes including spirometry, blood samples, anthropometry and administered questionnaires about respiratory symptoms. We used multivariable Poisson regression to assess biologic, socioeconomic and environmental risk factors associated with chronic bronchitis. Results: Overall prevalence of chronic bronchitis was 5.9% (95%CI 5.1%-6.9%) with variation by setting: prevalence was lower in semi-urban Tumbes (1.3%) vs. highly urbanized Lima (8.9%), urban Puno (7.0%) and rural Puno (7.8%; p < 0.001). Chronic bronchitis was more common among participants with vs. without COPD based on FEV₁/FVC< LLN (12.1% vs 5.6%, p < 0.01) and it was associated with increased reporting of dyspnea on exertion (p < 0.001), hospitalization (p = 0.003) and workdays missed due to respiratory symptoms (p < 0.001). Older age (Prevalence ratio [PR] = 1.23 for each 10-years of age, 95%CI 1.09-1.40) past history of asthma (PR = 2.87, 95%CI 1.80-4.56), urbanization (PR = 3.34, 95%CI 2.18-5.11) and daily exposure to biomass fuel smoke (PR = 2.00, 95%CI 1.30-3.07) were all associated with chronic bronchitis. Conclusions: We found important variations in the prevalence of chronic bronchitis across settings. Prevalence increased with both urbanization and with daily exposure to biomass fuel smoke. Having chronic bronchitis was also associated with worse patient-centered outcomes including dyspnea, hospitalization and missed workdays.