A population-based study of smoking, serum cotinine and exhaled nitric oxide among asthmatics and a healthy population in the USA
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BACKGROUND: Fractional concentration of exhaled nitric oxide (FeNO) is recommended by the American Thoracic Society (ATS) as a noninvasive biomarker of airway inflammation. In addition to inflammation, many factors may be associated with FeNO, particularly tobacco exposure; however, only age has been included as an influential factor for children below 12 years. Numerous studies have demonstrated negative associations between tobacco exposure and FeNO levels with self-reported data, but few with an objective assessment of smoking. METHODS: Data from the National Health and Nutrition Examination Survey (NHANES) 2007-2012 were analyzed to examine the association between FeNO and active/passive tobacco. Exposure was assessed by both self-report and serum cotinine levels among 11,160 subjects aged 6-79 years old with asthma, or without any respiratory disease. RESULTS: Study results indicated 28.8% lower FeNO, 95% CI [25.2%, 32.3%] and 38.1% lower FeNO, 95% CI: [28.1, 46.2] was observed among healthy and asthmatic participants with serum cotinine in the highest quartile compared to those in the lowest quartile, respectively. Self-reported smoking status and recent tobacco use were also associated with decreased FeNO. Self-reported passive smoking was significantly associated with a 1.0% decrease in FeNO 95% CI [0.0, 2.0] among asthmatic subjects but not among healthy subjects. CONCLUSIONS: Active smoking, whether measured by self-report or serum cotinine, was associated with decreased FeNO levels. In addition to age, increased attention should be given to tobacco exposure when using FeNO as a biomarker in clinical practice. Additional research is needed to establish reference value of FeNO considering the impact of tobacco exposure.
author list (cited authors)
Xu, X., Hu, H., Kearney, G. D., Kan, H., Carrillo, G., & Chen, X.