Biomarkers of early respiratory effects in smoking adolescents

Noninvasive biomarkers can be used to evaluate airways damage caused by tobacco smoke, but studies so far have only involved adult smokers. In this study, we evaluated whether such biomarkers can detect early respiratory effects in adolescents passively or actively exposed to tobacco smoke. In a cross-sectional study of 845 adolescents (mean age 16 yrs), we measured exhaled nitric oxide (NO) and various epithelial markers in nasal lavage fluid (NALF) and serum, including Clara cell protein (CC16) and surfactant protein (SP)-D. Information about smoking habits and potential confounders was collected by questionnaire. Four groups of equal size (n = 36), of nonsmokers, passive smokers, light smokers (<5 cigarettes · day(-1), median 0.08 pack-yrs) and heavy smokers (≥ 5 cigarettes · day(-1), median 0.35 pack-yrs), were matched using an automated procedure. The levels of exhaled NO and of CC16 in NALF were significantly decreased in the group of heavy smokers. A trend towards lower levels of CC16 in NALF was observed in passive smokers. There were no significant changes in serum CC16 and SP-D, which suggests that the deep lung epithelium had not yet been affected by smoking. In conclusion, tobacco smoke can cause early changes in the airways of adolescents with a cumulative smoking history of <1 pack-yr.