Eur Respir J
1989, 2,
470-472
SHORT REVIEW
Why are hospital admissions of children with acute asthma
increasing?
E.A. Mitchell*, K.P. Dawson**
Why are hospital admissions
of
children with acute asthma increasing?
EA.
Mitchell, K.P. Dawson.
• Dept
of
Paediatrics, University
of
Auckland,
Auckland, New Zealand.
ABSTRACT: The hospital admission
rate
for
as
thma has Increased in
many
countries. Particularly prominent has been the increase f
or
children,
especially male children und
er
five yrs.
The
increased
ad
mission
rate
re-
fers
to
increased number
of
individuals and to increased frequency
per
in-
dividual. The
mod
erate increase
to
asthma prevalence does not account for
the large Increase
In
admis.<;ions.
Various oth
er
factors are discussed here,
such as changes in admission criteria, medical manageme
nt
, and/or clini-
cal expression of the disease.
••
Dept
of
Paediatrics, Christchurch Hospital,
Christchurch, New Zealand
Correspondence: Or E.A. Mitchell, Dept of
Paediatrics, School
of
Medicine, University
of
Auckland, Private Bag, Auckland I, New Zealand.
Keywords: Admission criteria; asthma;
hospital
admission; prevalence; severity.
Eur Respir
J.,
1989, 2, 470-472.
Asthma poses a major health problem. This is well
illustrated
by
the high mortality rate in
ad
ults [1], al-
though fortunately an uncommon event in children (2];
the rising hospital admission rates for acute asthma
at
all ages [3-5); and the significant morbidity as meas-
ured
by days l
ost
from school or work [6].
Hospital admission rates for asthma in New Zealand
have increased notably in all age groups since the mid
1960's [3]. In five yrs (1976-1981) national admission
rates have almost doubled, and this increase has
occurred uniformly throughout the
co
untry [7].
The
increase is not restricted
to
New
Zealand, but is
an
in-
ternational phenomenon, although
New
Zealand and
Australia show the m
ost
striking increases
[8
-9]. Par-
ticularly prominent has been the increase in admission
rates for children, especially male children under five
yrs
[10--12].
Hospital admissions refer to events rather than indi-
vidual patients.
The
refore, these trends could possibly
be explained
by
a tendency
to
more frequent admissions
to hospital
of
t
hose
children who have established
asthma and have
an
exacerbation, thus boosting the
admission rates
by
numerous re-admissions. There
is
some
evidence from studies in New Zealand and
England that this is partially so, but the change is
in-
sufficient to account for the total increase in numbers
[4, 11].
There have been many attempts, over several years,
to establish prevalence rates for asthma. The surveys
have used a wi
de
variety
of
methodologies, which re-
flect the Jack
of
a firm definition
of
the condition.
The
Received: March, 1988: accepted after revision
November 19. 1988.
diagnosis
of
asthma has been variously based on ques-
tionnaire, examination, lung function tests and bronchial
chaJJenge tests. Unfortunately, the original hope that
bronchial challenge tests would
be
the gold standard for
the diagnosis
of
asthma has not been fulfilled [13].
Further confusion exists between
"w
heezing" and
"asthma" [14]. Several studies have suggested that only
a third
of
all children with histories
of
recurrent wheeze
have been labelled
as
having asthma [15-17].
The
prevalence
of
recurrent wheezing in western populations
has been variou
sly
reported
as
between 2 and 39% and
of
asthma between 2 and 18% [18].
SMITH
[19, 20] has
reported an increase in prevalence
in Birmingham,
England from
1.
8%
in 1957 to 6.3% in 1975, but this
increase could have been caused by a
cha
n
ge
of
defi-
nition. In Lower Hutt, New Zealand, an increase in the
reported prevalence
from 7.1% in 1969 [21] to 13.5%
in 1982 was found in the same two intermediate schools
using the same questionnaire [22]. Although this study
suggests that prevalence has increased
it
is
not definite,
as "asthma" may now be better recognized by the fam-
ily practitioner and parent than was the case in 1969.
However, even
if
the prevalence has increased it does
n
ot
read
il
y explain the huge incr
ease
in admissions.
Admission patterns could
be
influenced by change in
the
cr
iteria for admission to hospital as perceived by
the general practitioner or parents, such that more
chil-
dren with mild asthma are now referred for admission.
This has been studied, retrospectively,
in
both New
Zealand and England.
Two
of
the studies suggested that
the threshold for admission has remained unchanged
INCREASING ADMISSIONS
FOR
ASTHMA
471
[10, 23). One study suggested that the threshold has in-
creased, so that not only are there more children ad-
mitted
to
hospital but they tend to be more severely
affected [24). A recent study, using a clinical scoring
method for measuring severity, determined that
in
New
Zealand significantly more asthma admissions could be
graded as severe
or
very severe [25], compared with a
similar study
in
the UK after the application
of
the
same scoring method [26). Mild cases were, therefore,
not admitted disproportionately.
A further factor which
has
been implicated as the
cause for increasing severity and increasing hospital
admission rates is change
in
the medical management
of
asthma [27, 28]. There has been an impressive in-
crease in asthma drug sales
in
many countries [29).
There have also been major improvements
in
asthma
treatment in children, with better understanding
of
the
pharmacokinetics
of
asthma drugs, improved formula-
tions and better delivery systems. However, paradoxi-
cally this group has shown the greatest increase
in hospitalization. There is now a real concern that
sympathomimetics, whilst excellent for treating the
acute episode, may in fact be making asthma worse
in
the long run by increasing bronchial hyperresponsive-
ness [30-32].
The evidence presented here suggests that there has
been a small increase
in
asthma prevalence in children
with a dramatic increase
in
the number
of
children with
severe asthma requiring hospitalization. This could be
explained by either an increase
in
the proportion
of
the
population susceptible to asthma
or
by an increase
in
the clinical expression
of
the
di
sease by those who are
susceptible. This is illustrated in figure
1.
A shift
in
the
curve to the right
(A
to B) causes a small increase in
the proportion
of
the population (area under the curve)
with mild asthma but a much larger increase
in
the
proportion with severe asthma.
nil
mild
severe
Asthma severity
Fig.
1.
-
The
effect
oo
the
prevalence
of
mild
and
severe
asthma
caused
by
a s
mall
change
in
the
distribution
of
asthma
(A
to
B).
The increase in hospital admissions for asthma
in
children is real and
is
not explained by diagnostic trans-
fer, readmissions,
or
changes
in
admission criteria. The
uniformity of the increase within New Zealand
[7)
and
the smooth increase with time
in
all countries studied
[8)
suggests that whatever
th
e factor, it is operating
throughout the western world. Environmental factors
such as pollution
or
airborne allergens, which
may
have
produced this, seem unlikely culprits [33], but changes
in diet cannot be excluded [34]. Medical management
of
asthma must
be
examined more closely. In particu-
lar, long-term trials are needed comparing asthmatics
treated with regular sympathomimetics with those us-
ing sympathomimetics sparingly. The other major re-
search need is to answer conclusively whether
or
not
prevalence and severity
of
asthma is increasing.
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Pourquoi les hospitalisations d' enfants atteints d' asthme aigu
ausmentent-elles?
EA.
Mitchell, K.P. Dawson.
RESUME: Le taux d'hospitalisation pour asthme a augrnentc
dans de nombreux pays. Ceci fut particulierement le cas pour
les enfants surtout de sexe masculin
et
ages de moins de 5
ans. L'augrnentation du taux d'admission se rapporte
a
la
fois
a un nombre accru d'individus
et
a
Wle
frequence accrue par
individu. L'augrnentation
moderee
de
la prevalence de
l'asthme ne rend pas compte de
la
forte augmentation des
hospitalisations. D'autres facteurs, tels que les modifications
des
criteres d'admission, l'approche medicale,
et
!'expression
clinique de
la
maladie, sont envisages.
Eur
Respir J., 1989, 2, 471-473.
