How much asthma is there?

Is asthma increasing?

Between the 1970s and the 1990s asthma increased in the number of people with a diagnosis and the number of attacks that they were having. 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.

Since that time the increase has been much slower, but there has been no real evidence of a substantial fall in numbers affected. Gratifyingly, the rise stopped in the early 1990s and is now declining, although some markers of asthma remain high.

Asthma is the most common condition to be found in western populations, affecting over five million individuals in England and Wales alone. In children, boys are more likely to be affected than girls, while in adult life the condition is slightly more common in women.

Why did asthma increase?

It is possible that some of the increase mentioned above is a result of 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 treatments used for asthma itself – have all been blamed for the increase, but there is limited evidence to support these ideas.

More recently it has been suggested that the increase in asthma is related to a reduction in infections – in other words, the more germs there are the less asthma is likely to occur. This has been dubbed the ‘hygiene hypothesis’, the basic idea being that with our hygienic modern lifestyle our immune systems, having less need to respond to infection, respond to allergens thus leading to asthma. It has also been suggested that the various germs that live in our intestines may also play a role in determining whether we develop asthma.

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 adequate 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 in the north Pacific Ocean, 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 but where infections and parasitic infestations abound – further evidence to support the hygiene hypothesis.