HEALTH / Second opinion

IN MY time as a doctor most childhood diseases have become less common; many, such as measles, are now preventable by immunisation while others such as rheumatic fever have been eliminated by antibiotics and better nutrition. The exception is asthma. Around the world, surveys of children have consistently shown that the disease has become more frequent since the Second World War. In Britain and other Western countries one child in 10 now suffers asthma attacks. Fortunately, around half those affected get better as they grow older, but the others continue to wheeze throughout their adult lives.

Many chest physicians suspected atmospheric pollution from industry and traffic was to blame. Three gases in smoke and exhaust emissions - sulphur dioxide, nitrogen dioxide and ozone - irritate the nose, throat and lungs and cause wheezing and shortness of breath in people with asthma. But the evidence is conflicting.

When Germany was divided into East and West the two populations were genetically similar enough for their susceptibility to disease to be identical. For the 40 or so years of separation the citizens of East Germany were exposed to far higher levels of atmospheric pollution than their neighbours in the West. The population of East Germany coughed and spluttered its way through the winters - but relatively few of the children became asthmatic. Studies of children in the two Germanies have repeatedly shown that asthma is more common in the West. In one recent investigation of 6,000 children, the proportion with asthma in Leipzig was 7.3 per cent whereas in Munich it was 9.3 per cent. Even bigger differences have been found for the related allergic disorder, hay fever: around 13 per cent of people in Erfurt reported symptoms of nasal allergy as against 23 per cent in Hamburg.

Why should the affluent West Germans, concerned as they are to improve their environment, have such high rates of allergic diseases affecting their noses and lungs? A research report from Hamburg published in the September issue of Thorax suggests that the problem begins at home. Children in West German cities have high levels of antibodies against house-dust mites and cat fur - the most common household triggers of asthma. In a study of 900 schoolchildren the prevalence of these antibodies was three to five times higher in West German children than in their contemporaries in the East. No such differences were found in other antibodies such as those to grass pollens.

The culprit is, says the report, the Western housing style - double-glazed homes with high humidity and more indoor pets. Similar conclusions have been reached by researchers at Southampton University, who have also blamed the close-carpeted, stuffy houses in which so many children live for their chest problems. Parents of children with asthma are advised to vacuum away dust, clean carpets and bedding frequently, and keep pets out of bedrooms. Perhaps, too, there is something to be said for leaving bedroom windows wide open.