Trends in Hospital Admissions and Deaths from Asthma. 2002/1
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Introduction
This factsheet extends to 1999 the LAIA factsheets 96/2 on admissions
for asthma and 97/3 on asthma mortality. It describes trends in
asthma admission rates and death rates from 1979. This is the
year in which the International Classification of Diseases, 9th
revision (ICD 9) was introduced; ICD 10 was initiated in 1995
for admissions and in 2001 for deaths.
Hospital admission rates
Table 1: Percentage change in admission rates and mortality rates
This table shows the percentage changes in hospital admissions
from asthma in England and Wales over the 20 year period from
1979-1999. There was more than a doubling in admission rates among
the 0-4 age group. The other age groups also showed an increase
but to a lesser extent and with no trend with increasing age.
Figure 1:Trends in hospital admission
rates for asthma in children
Figure 2:Trends in hospital admission
rates for asthma in adults
The overall changes in admission rates conceal two opposing trends.
Until 1985, asthma admissions were increasing in all age groups
but from 1988, the trends were all downward. The gap in 1986 and
1987 corresponds to the change from the HAA to the HES system
(see factsheet 96/2), but there was no change in coding practice.
Figure 3:Trends in hospital admission
rates for asthma
In Scotland, where there has been no change in the information
system, asthma admission rates were comparable and showed a similar
increase in all ages in the earlier period. There has been a downturn
only in children, which occurred in the early 1990s, later than
in England and Wales.
Mortality
Trends in mortality show a different pattern. Overall, there
has been a decrease of about 40% in all age groups up to 65 years.
Figure 4:Trends in asthma mortality
rates
Figure 5:Trends in age-specific asthma
mortality rates
These asthma mortality trends show an increase in all adult age
groups followed by a gradual decline which occurred a few years
later in the 65+ age group. The irregular pattern for children
is explained by random variability due to the small numbers who
die of asthma in this age group, but there has also been an overall
decline. Neither the introduction of a revised interpretation
of Rule 3 in 1984 (a rule advising how to select the cause of
death, see factsheet 97/3) nor
its withdrawal in 1993 were associated with substantial step changes
across any age groups. This is indicative of a lack of any coding
effect.
Interpretation
Changes in coding and information systems are unlikely to explain
these trends. Hospital admissions can vary due to changes in medical
practice or patient behaviour. Other studies have shown that the
rising trend in admissions was not due to an increase in re-admission
rates or diagnostic transfer from related conditions. Admission
rates could also reflect changes in underlying morbidity. This
can relate to the prevalence of asthma itself or the prevalence
or severity of asthma exacerbations. There is evidence from general
practice of fewer asthma attacks (factsheet 2000/1)
and also evidence that suggests patients are being prescribed
more medication, both of which would correspond to this explanation
(factsheet 99/1). The underlying
prevalence of asthma may have also increased, but little is known
about trends in UK prevalence through the 1990s.
Mortality is related to incidence (cases and exacerbations),
severity and case fatality. Thus, the mortality trends could represent
changes in either the epidemiology or medical care of asthma.
It is tempting to speculate that the downturn in admissions and
mortality is due to improved management of asthma, but an underlying
change in epidemiology due to trends in unknown factors is also
possible.
Summary
-
There was a large increase in admission rates for asthma
during the 1980s.
-
Rates of admission have been falling since 1988 in all age
groups in England and Wales, but especially so in children.
-
Rates of admission have been falling in children in Scotland
since the early 1990s.
-
From 1979 to 1999, mortality rates from asthma have fallen
in England and Wales in all age groups.
Sources
Department of Health, Hospital In-patient
Enquiry and Hospital Episode Statistics
Health Solutions Wales, Bro Taf Health
Authority
Common Services Agency, Scotland, Hospital
discharges
Office for National Statistics, Mortality
Statistics
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