The short answer is – a lot! Up-to-date
estimates suggest that 20 per cent of children of primary school age
and around 6–7 per cent of the general population in the UK suffer
from asthma. It is the most common condition to be found in Western populations,
affecting over three million indiv-iduals in England and Wales alone.
In children, boys are twice as frequently affected as girls, while in
adult life the condition is slightly more common in women.
Is asthma increasing?
Asthma increased between the mid-1970s and the early 1990s, regard-less
of what measure of asthma you look at. For instance, over that period
there was around a fivefold increase in the numbers of patients presenting
to their GP with an attack of asthma, more so in children but to
some extent in adults. There was also an increase in hospital admissions
up to the early 1990s, again particularly in children, possibly reflecting
the fact that parents are more likely to seek medical advice for
their children than for themselves, although other factors are also
likely to play a part. Gratifyingly, the rise stopped in the early
1990s, and has fallen slightly since.
Why did asthma increase?
It is possible that some of the increase is due to doctors now using
the word ‘asthma’, whereas before they would have used ‘wheezy
bronchitis’, but this cannot explain the greater part of the rise.
Exposure to allergens in the home, viral infections, and aspects of
the indoor environment such as central heating, air pollution, the
stress of modern living – even the treat-ments used for asthma
itself –
have all been blamed for the increase.
More recently, it has been suggested that the reduction in infectious
diseases such as tuberculosis and measles in childhood has allowed the
body’s immune system to respond more to allergens. This has led
to the media description of this theory as the ‘hygiene’ hypothesis.
Deaths from asthma
Fortunately, death from asthma is not common. In the mid-1960s a short-lived
epidemic of deaths caused by asthma occurred, which some thought might
be the result of a toxic effect of one of the asthma inhalers on sale
at the time. This has been disputed over the years and other factors
may have been of importance; it is unlikely that we shall ever know
the complete story surrounding that event.
In fact, most asthma deaths are caused by undertreatment
of patients and it has been shown that two-thirds of asthma deaths would
have been preventable with ade-quate treatment.
Between the 1970s and the 1990s, there was a further
slight rise in asthma deaths in patients over the age of 50, although
this, again, settled down in the 1990s. Why this has occurred is not
clear, although in the older patient differentiating between asthma and
chronic bronchitis is often difficult and this may have led to a change
in diagnostic fashion.
Geographical differences
There are certainly some parts of the UK where asthma
admissions and GP attendances are more common, and other areas where
they are less so. However, the differences are modest and do not form
a clear-cut geographical pattern, unlike attacks of acute bronchitis,
which are higher in the north, becoming less so towards the south.
Although the differences within the UK are slight,
there are quite huge differences in the distribution of asthma in different
parts of the world. It is almost unheard of in Eskimos and black Africans
living in rural areas, whereas in the Western Caroline Islands nearly
50 per cent of the inhabitants have asthma, with three-quarters of all
children being affected.
Between these extremes are the Westernised populations,
such as people in the UK, Australia,
New Zealand and other European countries, which all
have roughly the same amount of asthma. Interestingly, those parts of
the world with less asthma are those that are less encouraging to the
survival of the house dust mite.
|
KEY POINTS
- Over three million individuals in England and
Wales alone have asthma
- Boys are more frequently affected than girls,
but the condition is slightly more common in women than in men
|
