Asthma after childhood pneumonia: six year follow up study
BMJ 2000; 320 doi: https://doi.org/10.1136/bmj.320.7248.1514 (Published 03 June 2000) Cite this as: BMJ 2000;320:1514
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Editor-
Clark et al. found that of 131 children recruited into their study, 35 had
asthma symptoms, an asthma diagnosis or had received asthma treatment
during six years follow up (1). This is presented as a cumulative
prevalence of 45%, which is significantly greater than previous studies
have shown. This figure may have resulted from bias in selection of more
symptomatic children during recruitment and follow up.
From the initial 131:
93 chest radiographs were reviewed
78 chest radiographs were agreed upon to show signs of pneumonia
35 of these cases had "any diagnosis of asthma", had received treatment
for asthma or had high symptom scores
35/131 represents a cumulative prevalence of 26.7%, considerably less than
the 45% quoted.
Children not included in follow up may not have had a chest
radiograph due to milder symptoms, may not have had changes on chest
radiograph but still have had pneumonia or may later have been entirely
symptom free and so not elected to attend any follow up. Those initially
recruited may have attended the authors' hospital after asthma selected
them for presenting with more severe symptoms.
The measurement of cumulative prevalence is not the best statistic to
employ in this situation as, of the age group studied 50% were under the
age of 4 years, an age when making a definitive diagnosis of asthma is
very difficult. Many children wheeze or cough as a result of viral
respiratory tract infection (2) or from being born with intrinsically
smaller airways that are more easily obstructed (3). Most of these
children will not retain a diagnosis of asthma yet in this study they are
included with those who do. Measuring point prevalence or using a measure
of morbidity that examines data over six months or a year such as a
symptom diary or the ISAAC questionnaire may have resolved this issue. The
epidemiological study of Martinez et al. (4) found that 48.5% of children
wheezed during their first six years but of these only 13.7% were wheezing
at three and still at six years. These figures illustrate that there is a
high frequency of transient non-asthmatic airways symptoms in younger
children. Further longitudinal studies following children in their
earliest years are needed to clarify which wheezing children will retain
or attain a diagnosis of asthma in later childhood and adulthood.
Simon Fearby
Clinical Research Fellow
J.B.Clough
Senior Lecturer in Child Health and Honorary Consultant
Paediatrician
Department of University Child Health,
Mail point 803,
Southampton General Hospital,
Tremona Road, Southampton
SO16 6YD
Competing interests: none
1. Clark EC, Coote JM, Silver DAT, Halpin DMG. Asthma after childhood
pneumonia: six year follow up study. BMJ 2000; 320: 1514-6.
2. Pattemore P, Johnston S, Bardin P et al. Viruses as precipitants
of asthma symptoms. Clin Exp Allergy 1992; 22: 325-36.
3. Martinez FD, Morgan W, Wright AL, Holberg C, Taussig LM, GHMA
Personnel. Diminished lung function as a predisposing factor for wheezing
respiratory illness in infants. New Eng J Med 1988; 319: 1112-7.
4. Martinez FD, Wright AL, Taussig LM, Holberg CJ, Halonenen
M, Morgan WJ and the Group Health Medical Associates. Asthma and Wheezing
in the first six years of life. N Eng J Med 1995; 332: 133-8.
Competing interests: No competing interests
Clark et al. (1) comment that "the cumulative prevalence of asthma
after childhood pneumonia is high; therefore careful follow up is
recommended to detect new cases."
Whilst I agrre with this sentiment I do not believe that they have
made an accurate diagnosis of pneumonia. They have not determined a
microbiological cause of pneumonia. Without it consolidation on a chest x-
ray, together with fever and taccyhpnea, might be confused with a viral
exacerbation of asthma and the radiological features of mucous plugging.
I believe they have highlighted an important message: keep an open
mind about radiological and clinical diagnoses of asthma versus pneumonia.
I do not think that they have demonstrated an association with pneumonia
and asthma.
10 Clark et al. Asthma and childhood pneumonia: six year foolow up
study BMJ 2000 320:1514-1516
Competing interests: No competing interests
Asthma afetr childhood pneumonia
EDITOR - Clarke et al claim their research demonstrates the
prevalence of asthma after childhood pneumonia is high, that pneumonias
may be an unrecognised presentation of asthma and that a structured
questionnaire may facilitate the recognition of asthma [1]. I would take
issue with these
conclusions based on two methodological problems. Firstly, the authors
claim a high cumulative prevalence of asthma (45%) 6 years after
pneumonia.
Without a control group it is impossible to be sure of this
interpretation.
The authors quote 2 major pieces of epidemiology showing an increase in
prevalence of asthma with age. Indeed, Martinez et al demonstrated that
approximately 50% of children suffer some form of wheezing in their first
6 years with 15% not developing wheeze until after 3 years of age [2]. An
alternative interpretation is that asthma is under-diagnosed and any
cohort of children, whether they suffered pneumonia or not, is likely to
pick up an increasing cumulative prevalence of asthma over time.
Secondly, the study relies on a questionnaire to diagnose asthma. This has
inherent problems, particularly in children. All that wheezes is not
asthma [3] and there are many different interpretations to the meaning of
'wheeze'.
It has recently been shown that some parents consider wheeze to be
whistling, squeaking or rasping; others define it as a different rate,
style or timbre of breathing, and some think it was the same as coughing
[4]. This may partly explain the apparent high cumulative prevalence of
asthma.
The report suggests childhood pneumonia may be an underrecognised
presentation of asthma yet there is no consideration of children with
pneumonia not admitted to hospital. Could it be that those predisposed to
asthma either genetically or because of early environmental factors, had
unrecognised airway abnormalities (e.g. bronchial hyperresponsiveness)
making them more likely to require hospital admission with pneumonia than
non-asthmatics?
The link between early childhood infections and later atopic illnesses is
of great interest. The 'hygiene hypothesis' suggests that increased
frequency of childhood infections is not associated with atopic asthma
[5]. This adds weight to the possibility that asthmatics become more
unwell during the illness rather than pneumonia per se being associated
with asthma.
Michael Mckean
specialist registrar in paediatric respiratory medicine Children's
Hospital
Leicester Royal Infirmary
Leicester
LE2 7LX
References
1. Clark CE, Coote JM, Silver DAT, Halpin DM. Asthma after childhood
pneumonia: six year follow up study. BMJ 2000; 320: 1514-1516.
2. Martinez, F.D., Wright, A.L., Taussig, L.M., Holberg, C.J.,
Halonen, M.,Morgan, W.J., Bean, J., Bianchi, H., Curtiss, J., Ey, J.,
Sanguineti, A.,Smith, B., Vondrak, T., West, N., and McLellan, M. Asthma
and wheezing in the first six years of life. New England Journal of
Medicine 1995;332(3):133-138.
3. Silverman, M. Out of the mouths of babes and sucklings: lessons
from early childhood asthma. Thorax 1993; 48:1200-1204.
4. Cane RS, Ranganathan SC, McKenzie SA. What do parents of wheezy
children understand by "wheeze"? Archives of Dis. Childhood 2000; 82(4):
327-32.
5. Von Mutius, E., Illi, S., Hirsch, T., Leupold, W., Keil, U., and
Weiland,S.K. Frequency of infections and risk of asthma, atopy and airway
hyperresponsiveness in children. European Respiratory Journal 1999;
14(1):4-11.
Competing interests: No competing interests