Health Effects of Childhood Exposure to Environmental Tobacco Smoke in Children followed to Adulthood

Abstract

Background A significant proportion of children are exposed to environmental tobacco smoke (ETS) throughout the world. This is mainly because of exposure to parental smoking. It is unknown to what extent the negative effects of ETS on respiratory symptoms track from childhood into adulthood. Methods TESAOD (Tucson Epidemiologic Study of Airway Obstructive Disease) is a large population-based prospective study that was initiated in 1972. Participants were followed prospectively with questionnaires and pulmonary function tests (PFTs) completed about every two years in 12 follow-up surveys up to 1996. Skin prick tests and blood samples for IgE measurements were collected at surveys 1, 6, and 11. We identified subjects who entered the study as children (<15 years old) and were followed to adulthood (>18 years) during the study follow-up. Based on questionnaire data, active asthma, wheeze, cough, and chronic cough (cough for three consecutive months) were coded as never (never reported in childhood or adulthood), incident (never reported in childhood, but ≥ one positive report in adulthood), remittent (≥ one positive report in childhood, but not in adulthood), and persistent (≥ one positive report both in childhood and adulthood). PFTs measurements included forced expiratory volume in 1 second, forced vital capacity, and forced expiratory flow at 25-75%. Parent information on smoking status was collected simultaneously at child visits. ETS exposure status was assessed as “ever” or “never” between birth and 15 years. Results Information on parental ETS exposure in childhood and outcomes in adulthood was available for 444 non-Hispanic white participants (51.4% male) with mean age at initial survey of 7.7 years. Total mean follow-up time was 19.0 years (8.8 years in adulthood). Between birth and 15 years, 53.4% of children were exposed to ETS. After adjusting for sex, age at enrollment, years of follow-up, and personal smoking status (assessed at age 15 and above), combined parental ETS exposure in childhood was significantly associated with persistent wheeze (RR(adj) 1.9, p=0.026), persistent cough (RR(adj) 5.9, p<0.001), and persistent (RR(adj) 3.7, p=0.030) and incident chronic cough (RR(adj) 2.3, p=0.040). Paternal ETS exposure in childhood was associated with persistent wheeze (RR(adj) 2.3, p=0.002), persistent cough (RR(adj) 3.9, p<0.001), persistent (RR(adj) 4.8, p=0.004) and incident chronic cough (RR(adj) 2.2, p=0.031), and persistent asthma (RR(adj) 2.3, p=0.016). Maternal ETS exposure was associated with persistent (RR(adj) 1.9, p=0.029) and incident cough (RR(adj) 2.5, p=0.006). Maternal ETS exposure was associated with an increased percent predicted FVC in adulthood (coefficient, 3.75; p=0.019). No other effects on lung function were seen. There were no effects of ETS exposure on total serum IgE or allergic sensitization. ETS exposure was associated with respiratory symptoms in adulthood among both never and current smokers. Conclusions ETS exposure in childhood has long term health effects on lung function and respiratory symptoms. These effects do not appear to be IgE-mediated. ETS exposure, especially paternal ETS exposure, seems to influence the persistence of respiratory symptoms from childhood to adulthood and to affect women more than men. These effects are independent of personal smoking and also seen in never smokers. Both smoking mothers and fathers should be targeted when attempting to reduce ETS exposure among children.