In the Sixties and Seventies, when I was a child, asthma was an exotic complaint. There was just a handful of other children at school who wheezed during PE. From late autumn, we would be off school for weeks and return, after an attack, looking distinctly wobbly. A place in the football team or the swimming squad was a great achievement.
In a couple of decades, all that has changed. Today, the classroom cupboard filled with blue and brown inhalers is a common site. About one in eight children in the UK has been diagnosed with asthma and last week, a study published in the British Medical Journal suggested that the problem might be even worse than we thought.
A survey of 12- to 14-year-olds found that one in three respondents had wheezed during the previous 12 months, although only half of those had been given the dreaded diagnosis. The researchers concluded that six or seven pupils at each large secondary school suffer moderate to severe symptoms, but are undiagnosed and untreated.
These figures suggest not just an ordinary disease, but an epidemic. They inevitably raise suggestions of hypochondria. Are over-zealous doctors exaggerating the problem, filling a generation with drugs - and the coffers of the pharmaceutical empires at the same time? Should we worry that what once might have been disregarded as a harmless cough has become the starting point of long and unnecessary treatment?
Scepticism is fuelled by the failure of science to establish why we should suddenly face such an epidemic. For a while, everyone blamed pollution. But publication of last week's study, involving 27,000 British school children, suggested that neither pollution, climate nor diet is the chief culprit - incidence is broadly spread and slightly higher in the clear pure air of the rural areas than in the cities.
So what do we really know about an illness that can be terrifying when a child suddenly gasps for breath? (Asthma actually kills 1,500 people a year in Britain, although a tiny fraction of this number is young.)
Asthma is the chronic inflammation of the airways, which leaves them hyper-responsive. As a result, they narrow readily when exposed to a wide range of triggers, including house dust mites, animal dander, damp spores, chest infections, smoke, stress, pollen and specific foods. Asthma represents something going wrong with the immune system, which for some reason starts to react to substances which most people find benign.
Secondly, the epidemic is real. If you need proof, visit the casualty unit of any children's hospital on a winter's evening and watch the steady stream of listless toddlers, their tired faces covered with a mask as a fine spray of anti-asthma drugs is administered.
Medical opinion is virtually united in seeing the current incidence of childhood asthma as around 15 per cent in Britain, far higher than in the recent past and some other countries. And it is rising. "There are now numerous studies pointing to this sort of figure," says Martyn Partridge, consultant chest physician at Whipps Cross hospital, London, and chief medical advisor to the National Asthma Campaign.
A sound diagnosis of asthma with well-targeted treatments can be highly beneficial to a child. Far better than doctors prevaricating, endlessly calling the problem a chest infection and wrongly prescribing antibiotics.
Nevertheless, you should not assume that a child's wheeze is necessarily asthma. It could just be a cold or bronchiolitis. Croup, which involves wheeziness, barking cough and breathlessness can mimic asthma and, although it usually clears up after a week, can recur. Asthma is notoriously hard to diagnose in children under two. Half of those under five who have wheezy illness will not have asthma when over five. So they either did not have the disease in the first place or they grew out of it. Those who develop asthma after the age of five are much less likely to grow out of it, says Dr Partridge.
Symptoms, which should, however, make you raise the question of asthma with your GP include: repeated bouts of wheezing, a persistent dry irritating cough, sleep disrupted by coughing or wheezing, shortness of breath after exercise.
We also know who is most in danger of developing disease. An immediate family history of allergic diseases, such as eczema, hay fever and asthma, is a very high risk factor, according to the recently published Which? Guide to Managing Asthma (Penguin pounds 9.99). Other risk factors are sex (boys are more vulnerable than girls); birth weight under 2.5kg; early contact with allergens (a child born between October and January is more likely to be allergic to house dust mite); passive smoking; diet (babies breast- fed for six months have much reduced incidence of asthma); teenage pregnancy (possibly due to high levels of allergen antibodies in adolescents); being first born (children with older brothers and sisters are exposed to more viral infections early in life, which are believed to offer protection against asthma).
Given this knowledge, is it possible to prevent the disease in children? Perhaps, we can stop some cases. Research is beginning to indicate that mothers exposed to high levels of some allergens, such as house dust mite, tobacco smoke, pollen, nuts, eggs and milk, may prime the babies' immune system. So some doctors advise women with a history of allergies to avoid large amounts of nuts and other allergens, particularly in the last three months of pregnancy. But this is no insurance against asthma.
What then can be done for children who already have asthma? Many people try clearing their homes and diets of potential allergens. But these irritants are so common in the environment and in diet that this is extremely difficult. And poor diet carries its own risks. So the current focus lies in managing the problem: controlling the inflammation of the airways. The main protection is an anti-inflammatory inhaler or "preventer" (based on a steroid, which suppresses the immune-response).
"There is increasing evidence," says Dr Martyn Partridge, "that the damage to the lungs caused by asthma may occur early on in the disease. So the indications are that aggressive treatment in the early stages of the disease will pay off." Hence the rush to diagnose the young.
Sufferers also use a "bronchodilator" (the blue puffer) which opens up the airways temporarily without reducing the underlying inflammation. Doctors are cautious about the long-term use of these inhalers because they mask the underlying disease, which can worsen without other treatment. There are also claims among a minority of chest experts that indiscriminate, long-term use of bronchodilators can actually damage the lungs and may have contributed to the high level of adult fatalities.
The big question is whether we can stop the massive increase in asthma cases. A vaccine to stop the body reacting to some allergens is a possibility. But, in the short-term, progress in curing the illness is hampered because pharmaceutical companies spend mainly on developing lucrative new drugs to manage the disease. And, although we understand many of the triggers for asthma, we still don't know what actually causes it.
"This is a disease of civilisation," says Dr Partridge. "I think we will find eventually that there are several genetic predispositions to asthma and that the likelihood of these being activated are increased by several factors - Mum smoking, the fall-off in exposure to infectious diseases, plus changes in the indoor environment." But for now, there is little a breathless child can do but keep taking that puffer and hope to grow up and out of asthma.
Asthma - the childhood signs:
Repeated coughing attacks: three quarters of children with recurrent or chronic coughs are eventually diagnosed as having asthma. But it could be croup, a viral infection or pertussis infection (which causes whooping cough).
Wheezing: about a third of children have at least one wheezing episode in their first two years of life, especially between two and six months. But they may not have asthma - almost a third of them never have another attack. Asthmatic children wheeze between colds, while healthy children recover after a few days.
Sleep broken by coughing and wheezing: 50 per cent of children with asthma suffer disturbed sleep every night.
Breathlessness after exercise or exertion
Does my child need an inhaler?
Yes, if the above symptoms persist. If asthma goes untreated, it can deteriorate. Children will tend to withdraw from sport and lead a sedentary lifestyle. Repeated attacks can damage childhood growth. Treatment will normally focus on an anti-inflammatory inhaler (usually steroid-based) reducing the number of attacks. Use of bronchodilator inhalers should be confined to acute episodes.
Are inhaled steroids safe for children?
They may slightly inhibit growth in some children, but uncontrolled asthma will do so far more. At normal dose levels, studies indicate that neither growth nor resistance to infection is damaged by inhaled steroids. They should be taken regularly even when the child is well.
Source: `The Which? Guide to Managing Asthma' (Penguin, pounds 9.99)