Lower respiratory tract symptoms in Queensland schoolchildren: risk factors for wheeze, cough and diminished ventilatory function.

The occurrence of respiratory symptoms and abnormal lung function in children is known to be influenced by genetic and many environmental factors. The association between specific respiratory symptoms in children of school age and their parents has been examined. Respiratory symptoms and ventilatory function were recorded for 4549 schoolchildren in Queensland, Australia. The cumulative prevalence of wheezing was 23.1% of 8 year olds and 20.8% of 12 year olds, and the prevalence of wheezing within the previous 12 months was 13.9% and 10.5% respectively. A parental history of asthma or wheeze and hayfever was associated with wheeze in the child, but did not affect either the age of onset or frequency of episodes. A history of frequent cough in children who had never wheezed was associated with a parental history of frequent bronchitis, but less strongly with parental wheeze. These familial aggregations were not mediated by common exposure to cigarette smoke. Both a history of parental wheeze and maternal cigarette use were associated with a decrease in FEF25-75 in the child and these effects were additive. The association of specific symptoms (wheeze and cough without wheeze) in parent and offspring is interpreted as evidence for different mechanisms of familial transmission, which may be genetic.