A critical analysis of the relationship between parental smoking and pulmonary performance in children

To date, at least 24 epidemiologic research papers, of essentially similar design, have been published on the effects of current or lifetime parental smoking on pulmonary function parameters in children. In these studies, parental smoking and other data obtained from standardized questionnaires and spirometric measurements in children were compared statistically according to the smoking status of the parents. A survey of these reports reveals a number of inconsistencies in the association between parental smoking status and pulmonary function parameters (FEV1 or FEV0.75, FEF25-75, FVC, and Vmax50%) in the child. A number of factors should be considered when interpreting the results of these studies, particularly in light of the observed inconsistencies and the fact that children were classified solely on the basis of questionnaire data. Among these are sources of misclassification bias, which could either underestimate or overestimate parental smoking effect, socioeconomic status, other variables, and genetic factors. Also, effects of maternal smoking in utero or on lactation, as well as exposure of the child to environmental tobacco smoke (ETS), need to be considered as possible causes of any apparent decrement in pulmonary function in children.