Elastin degradation markers are elevated in never-smokers with past history of prolonged exposure to secondhand tobacco smoke and are inversely associated with their lung function

Background Prolonged past exposure to secondhand tobacco smoke (SHS) in never-smokers is associated with occult obstructive lung disease and abnormal lung function, in particular reduced diffusing capacity. Previous studies have shown ongoing SHS exposure to be associated with increased elastin degradation markers (EDM) desmosine and isodesmosine. Research Question Are EDM levels elevated in persons with remote history of SHS exposure, and are those levels associated with reduced lung function? Study Design and Methods We measured the plasma levels of EDM from 193 never-smoking flight attendants with history of remote but prolonged SHS exposure in aircraft cabin and 103 nonsmoking flight attendants or sea-level control participants without history of cabin SHS exposure, and examined those levels versus their lung function with adjustment for covariates. The cabin SHS exposure was estimated based on airline employment history and dates of smoking ban enactment. EDM plasma levels were quantified by high-performance liquid chromatography and tandem mass spectrometry. Results The median [interquartile range; IQR] plasma EDM level for all participants was 0.30 [0.24 to 0.36] ng/mL with a total range of 0.16 to 0.65 ng/mL. Plasma EDM levels were elevated in those with history of exposure to cabin SHS compared to those not exposed (0.33±0.08 vs. 0.26±0.06 ng/mL; age- and sex-adjusted P<0.001). In those with history of cabin SHS-exposure, higher EDM levels were associated with lower diffusing capacity (parameter estimate (PE) [95%CI]=4.2 [0.4 to 8.0] %predicted decrease per 0.1 ng/mL increase in EDM; P=0.030). Furthermore, EDM levels were inversely associated with FEV 1 , FEV 1 /FVC, and FEF 25-75 (PE [95%CI]=5.8 [2.1 to 9.4], 4.0 [2.2 to 5.7], and 12.5 [5.8 to 19.2]% predicted decrease per 0.1 ng/mL increase in EDM, respectively) (P<0.001). Interpretation Prolonged past exposure to SHS, even when remote, is associated with higher systemic elastin degradation markers that in turn is associated with lower lung function and in particular reduced diffusing capacity.