The role of geographical and environmental exposures in respiratory infections among individuals with cystic fibrosis: A systematic review and meta-analysis.

BACKGROUND & AIMS: Chronic, recurrent respiratory infections are a hallmark of Cystic Fibrosis (CF). Previous reviews concluded that environmental and community risk factors likely interact with the respiratory tract in CF. However, these studies do not include a systematic search, quality and risk of bias assessment, or meta-analysis. This study aimed to: (i) systematically identify and summarise evidence on associations between environmental and geographical exposures and respiratory infections in CF from epidemiological studies, (ii) assess methodological quality and risk of bias of identified studies, (iii) synthesise evidence via meta-analyses. METHODS: Three electronic databases were searched to identify studies conducted in humans and published in English between 2014 and 2024 inclusive. All stages of study screening, data extraction, quality assessment, and risk of bias assessment were conducted in duplicate by independent reviewers. Meta-analysis was conducted when three or more estimates were available for an exposure. RESULTS: A total of 43 studies were included in this review. Weather season, vapour pressure, water and soil constituents, and air pollution were associated with bacterial respiratory infections but showed mixed associations with fungal and viral infections. Geographical exposures, including treatment centre location and residential location, were associated with both bacterial and fungal infections. CONCLUSION: Environmental exposures showed stronger associations with bacterial than fungal or viral infections, whereas geographical exposures were linked to both bacterial and fungal pathogens. These patterns suggest external factors act differently across infection types in CF. Acknowledging this may improve clinical risk stratification, but more standardised and geographically diverse research is needed.