Longitudinal study of childhood wheezy bronchitis and asthma: outcome at age 42

Participants, methods, and results

In 1964, 401 children (295 with asthma and 106 controls) were randomly selected from a total of 30 000 7 year olds living in metropolitan Melbourne. A further 83 children with severe asthma were included from the same cohort in 1967, at age 10. 2 3 Original data were available for 479 participants.

At recruitment, 105 children were classified as controls (children who had never wheezed); 74 had mild wheezy bronchitis (<5 episodes of wheezing associated with respiratory tract infection); 104 had wheezy bronchitis (≥5 episodes of wheezing associated with respiratory tract infection); 113 had asthma (wheezing unassociated with respiratory tract infection); and 83 had severe asthma (onset of asthma symptoms before 3 years of age, persistent symptoms at age of 10, and barrel chest deformity or ratio of forced expiratory volume in one second to forced vital capacity ≤50%).

At each review from the age of 21, participants were classified as follows: no recent asthma (no wheeze in past three years); infrequent asthma (wheezing in past three years but none in past three months); frequent asthma (wheezing in past three months, but less than once a week); or persistent asthma (wheezing in past three months, more than once a week).

Fifteen of the original cohort had died at follow up, one from asthma. Of the remaining 464, 403 participated in the current review, giving a continuing participation rate of 87%. In all, 267 participants attended the laboratory for measurement of lung function. We calculated mean values of lung function using standard two sample t tests and confidence intervals of the mean by standard methods.

The table shows the clinical expression of asthma at age 42 according to severity of disease at recruitment. The distribution of severity at age 42 has not changed from that at age 35.5 The proportion of cases with no recent asthma has increased steadily from 20% at age 14 years to 40% (126/317) at age 42.

Lung function was similar to that of controls in participants who had had wheezy bronchitis in childhood (table). Participants who had had asthma aged 7 had reduced lung function at age 42.

Comment

Our study shows that the pattern of asthma during childhood predicts outcome. Most children with persistent asthma had continuing symptoms into adult life and reduced lung function. However, children who had intermittent symptoms associated with respiratory tract infections generally had complete resolution of symptoms in adult life. The small number of participants who still had mild, intermittent symptoms at age 42 had normal lung function. This good outcome was achieved despite the fact that anti-inflammatory treatments were not available for most of their childhood.