Tobacco Smoke Exposure and Socioeconomic Factors are Independent Predictors of Pulmonary Decline in Pediatric Cystic Fibrosis

Abstract

Background: Few studies have attempted to disentangle the effects of tobacco smoke exposure and socioeconomic factors on lung function decline in pediatric CF. The current study evaluates their contributions longitudinally across the entire U.S. CF care network population. Methods: Data from the CF Foundation Patient Registry were obtained on all individuals who at the end of 2016 were 6-18 years old. Lung function measures (median, highest, and lowest ppFEV1) for each person were calculated at each attained age. Multivariable analyses used mixed modeling to assess the impact of smoke exposure and socioeconomic factors on both initial lung function and change over time. Findings: The sample included 10,692 individuals contributing 57,888 person years. At age 6, ppFEV1 of smoke-exposed children was 4% lower than among unexposed. The deficit persisted through age 18. In fully adjusted mixed models, smoke exposure and socioeconomic factors had independent, additive associations with lung function. Median ppFEV1 declined 2% with smoke exposure, 3% with lower paternal education, 1% with public insurance, and increased 0.2% with each $10,000 annual household income. The effect of smoke exposure on ppFEV1 was larger in disadvantaged children compared to privileged counterparts (2.5% vs 1.5%). Interpretation: Smoke exposure and socioeconomic factors are independent risk factors for decreased ppFEV1 in pediatric CF. Strategies to reduce smoke exposure should be introduced early. Interventions may be prioritized in disadvantaged children, among whom the exposure has a disproportionately large effect. Funding Statement: This study was supported by grants from NIH (P30DK72482, K08HL140190), AHRQ (K12HS023009), and CFF (CC032-14). Declaration of Interests: The authors have no conflicts of interest. Ethics Approval Statement: Written informed consent was obtained from all participants. The study was approved by the Institutional Review Board of the University of Alabama at Birmingham (protocol number 300002076).