Risk factors for childhood respiratory disease. Analysis of pulmonary function

Four thousand elementary-school-age children from a rural area of western Pennsylvania participated in a cross-sectional survey that consisted of a standardized respiratory questionnaire completed by their parents and spirometric testing at school. Spirographic tracings were digitized to obtain the FVC, FEV_0.75, FEF_25-75, V̇max₇₅, and V̇max₉₀, which were standardized for height, age, and sex for the subsequent analyses. Independent associations' of potential risk factors with the standardized pulmonary function measures were evaluated with multiple regression techniques. Asthma, persistent wheeze, and parental smoking habits, especially those of the mothers, were associated with lower flow rates. The effect of parental smoking was primarly due to smoking by the mother and was stronger in girls. In female children of currently smoking mothers, FEF_25-75 was 96% of predicted, V̇max₇₅ was 95% of predicted, and V̇max₉₀ was 92% of predicted; each flow measure was 98% of predicted in male children of smoking mothers. Prolonged hospitalization at birth was independently associated with lower FEV_0.75 and flow rates. Low socioeconomic status was associated with lower FVC and FEV_0.75. Neither current gas stove use nor a history of severe chest illness before 2 yr of age were independently associated with lower levels of pulmonary function.