The UCLA population studies of chronic obstructive respiratory disease. VII. Relationship between parental smoking and children's lung function.

Results of previous studies of the impact of parents' smoking on children's lung function have been conflicting. To evaluate further the effect of passive smoking on the lung function of children, we analyzed respiratory questionnaire and lung function results obtained during field testing of residents (aggregated according to household) of 4 census tracts in the Los Angeles area. We report here on 971 white, non-Hispanic, nonsmoking, nonasthmatic children residing in households in which the smoking status of both parents was known; households with ex-smoking parents were excluded from analysis. We divided these children into 3 categories related to parental smoking status: (1) at least mother smokes , (2) only father smokes , and (3) neither parent smokes . Prediction equations for several indexes of forced expired volume and flow were derived separately for boys and girls 7 to 17 yr of age. Analysis of variance was used to compare lung function residuals of children in the 3 different passive smoking categories. Analysis was performed separately on younger (7 to 11 yr of age) and older (12 to 17 yr of age) children of each sex. Among younger male children, residual values were significantly lower in the maternal smoking category than in the other 2 household categories for maximal flow and maximal flow after exhalation of 25% of forced vital capacity (FVC) (p less than or equal to 0.05); no differences were noted between the paternal-smoking only and nonsmoking household categories. A trend toward similar results was found in older male children, which approached significance (p less than 0.1). Among females, forced expiratory flow during the middle half of the FVC and maximal flow after exhalation of 75% of FVC were significantly lower in relation to maternal smoking in the older children only (p less than or equal to 0.05). ANOVA revealed no decrement in lung function in relation to passive smoking among children with asthma or bronchitis (n=138).(ABSTRACT TRUNCATED AT 250 WORDS)