Risk factors for age at initial Pseudomonas acquisition in the cystic fibrosis epic observational cohort

Background: Risk factors for initial Pseudomonas aeruginosa (Pa) acquisition, particularly environmental exposures, are poorly understood. We aimed to identify such risk factors in order to inform prevention strategies and identify high-risk populations. Methods: The study cohort included all participants in the U.S. EPIC Observational Study who had no prior Pa-positive respiratory cultures (N. =889). Cox proportional hazard models were used to test the effects of factors on age at first Pa-positive respiratory culture. Results: Cystic fibrosis (CF) genotype functional class had an important effect on age at initial Pa acquisition (hazard ratio (HR) comparing minimal to residual CFTR function 2.87 (95% CI 1.88, 4.39)). None of the modifiable risk factors evaluated, including cigarette smoke, hot tub use, breastfeeding, or daycare, was associated with age at Pa acquisition. Similarly, newborn screening was not associated with age at Pa acquisition (HR 0.85, 95% CI 0.66, 1.09). Key associations were validated in a CF Foundation National Patient Registry replication cohort. Conclusions: Given the ubiquitous presence of Pa in the environment, it may be that many imposed lifestyle changes will have less impact on age at initial Pa acquisition than genetic determinants.