Papers

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

Elisabeth Horak, research fellow ^a, Anna Lanigan, research assistant ^a, Mary Roberts, research assistant ^a, Liam Welsh, research assistant ^a, John Wilson, associate professor ^c, John B Carlin, deputy director ^b, Anthony Olinsky, director ^a, Colin F Robertson, associate professor ^a. 

^a Department of Respiratory Medicine, Royal Children's Hospital, Parkville 3052, Australia, ^b Clinical Epidemiology and Biostatistics Unit, Murdoch Children's Research Institute, Parkville 3052, Australia, ^c Department of Respiratory Medicine, Alfred Hospital, Melbourne, Australia

Correspondence to: C F Robertson colin.robertson{at}rch.org.au

Longitudinal studies have reported that asthma in childhood has a good prognosis. However, most of these studies have not taken into account the severity of childhood symptoms.¹ The Melbourne Epidemiological Study of Childhood Asthma recruited children at age 7 years and followed them up through adolescence to adulthood.^2-5 This report describes outcome at age 42 years in relation to symptoms in childhood.

	Participants, methods, and results

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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

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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.

	Acknowledgments

Contributors: CFR, AO, and JW initiated the project and, together with EH, AL, MR and LW, developed the protocol. EH, AL, MR, and LW were responsible for recruitment, data collection, and data analysis. JBC was the statistician. The manuscript was jointly written and reviewed by all of the authors. CFR is the guarantor.

	Footnotes

Funding: National Health and Medical Research Council of Australia. EH was funded by Nationalbank, Austria.

Competing interests: None declared.

	References

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1.	Ahmed IH, Samet JM. The natural history of asthma. In: Murphy S, Kelly HW, eds. Pediatric asthma. , Vol 126 New York: Marcel Dekker, 1999:41-69.
2.	Williams HE, McNichol KN. Prevalence, natural history and relationship of wheezy bronchitis and asthma in children: an epidemiological study. BMJ 1969; iv: 321-325.
3.	McNichol KN, Williams HB. Spectrum of asthma in children. I. Clinical and physiological components. BMJ 1973; iv: 7-11.
4.	Kelly WJ, Hudson I, Phelan PD, Pain MC, Olinsky A. Childhood asthma in adult life: a further study at 28 years of age. BMJ 1987; 294: 1059-1062[Abstract/Free Full Text].
5.	Oswald H, Phelan PD, Lanigan A, Hibbert M, Bowes G, Olinsky A. Outcome of childhood asthma in mid-adult life. BMJ 1994; 309: 95-96[Free Full Text].

(Accepted 7 November 2002)