Environmental Tobacco Smoke Affects Lung Function of Preschoolers With Asthma Even After a Decade

Abstract

To evaluate whether early tobacco smoke exposure has a long-term effect on lung function.Children (n = 105; mean age: 5.62 years) with a history of wheeze and bronchodilator response had been previously enrolled for a study evaluating the association between maternal smoking and preschool asthma. Children could not have taken corticosteroids in the previous 6 months nor have had a respiratory tract infection in the previous 2 weeks. These children were evaluated at a follow-up visit 10 years after the initial enrollment (n = 64; mean age: 14.22 years).The cohort in this study had been assessed at enrollment for environmental tobacco smoke exposure by urinary cotinine and questionnaires. At both enrollment and the 10-year follow-up, fractional exhaled nitric oxide (FeNO), impulse oscillometry (IOS), blood eosinophil counts, and allergic sensitization to indoor and outdoor aeroallergens were assessed. At the 10-year follow-up, children also performed spirometry and a methacholine challenge. Results were compared between enrollment and follow-up.At the 10-year follow-up, fewer children wheezed in the previous year (11% vs 83%), whereas more children had positive allergy testing results (92% vs 70%). Blood eosinophil count, FeNO, and total respiratory system resistance (resistance at 5 Hz [R5]), one of the IOS indices, were all decreased at follow-up. Forty-three percent of parents stopped smoking during the 10 years. Approximately one-third of children reported asthma symptoms and the need for asthma medications in the previous 2 months at the follow-up visit. None reported smoking. Being overweight correlated with forced expiratory volume in 1 second and/or forced vital capacity and the IOS indices (R5 and area under reactance), at the follow-up visit but did not correlate with the preschool urinary cotinine levels. However, preschool urinary cotinine levels did significantly correlate with increased FeNO scores, blood eosinophils, and R5 and decreased reactance (by 5) at the follow-up. No significant correlation was seen with forced expiratory volume in 1 second or methacholine challenge.Early tobacco smoke exposure is linked to the presence of airway inflammation and decreased lung function in older children with a history of asthma.Limitations included the lack of a control asthma group without preschool exposure to tobacco smoke, the small sample size, and lack of interval assessment during the 10-year period to evaluate the potential confounding effect of other environmental factors, socioeconomic factors, or the development of other comorbidities. The study also did not consider whether aeroallergen sensitization had an impact on lung function over time. IOS is not as commonly performed as spirometry for the assessment of asthma, so the use of IOS in assessing and managing asthma in a clinical practice needs further validation. Nevertheless, this study provides further proof that early exposure to tobacco smoke in childhood potentially has long-term negative health effects.