Salivary Cotinine, Doctor-diagnosed Asthma and Respiratory Symptoms in Primary Schoolchildren

Due to impaired airway function, children are at risk for adverse respiratory symptoms if exposed to environmental tobacco smoke (ETS). A community-based, cross-sectional study of 425 children (5–11 years) attending 15 primary schools in a low socio-economic area of Merseyside/UK was undertaken to investigate the association of adverse respiratory symptoms and ETS exposure using a parent-completed questionnaire and children’s salivary cotinine measurements. Overall, 28.9% of children had doctor-diagnosed asthma (DDA) and 11.3% a history of hospital admission for respiratory illnesses. The symptom triad of cough, wheeze and breathlessness (C+W+B+) occurred in 12.6% of children. The geometric mean cotinine level was 0.37 ng/ml (95% CI, 0.33–0.42 ng/ml) and it was estimated that 45.6% of children were ETS exposed. A history of asthma in the family was reported for 9.2% of fathers and 7.2% of mothers. Salivary cotinine level was significantly increased in children with DDA compared to those without (P = 0.002). Cotinine-validated levels [adjusted odds ratio (AOR), 1.8; 95% CI, 1.4–2.5), low socio-economic (disadvantaged) status (AOR, 1.4; 1.1–2.9), child’s male gender (AOR, 1.6; 1.1–2.5) and maternal smoking (AOR, 2.2; 1.4–3.1) were significantly associated with DDA. The cotinine-validated level (AOR, 1.4; 1.1–2.9) as well as maternal smoking (AOR, 1.8; 1.1–2.5), were also independently associated with C+W+B+. The use of salivary cotinine as an indicator of ETS exposure could be used to inform parents of exposure risk to their asthmatic children and may help re-enforce deterrent efforts to reduce childhood parental smoking exposure.