There has been a huge increase in asthma in Western countries since the early 1960s. Asthma currently kills nearly 2000 people a year in England and Wales yet in 1929, Conybeare's Textbook of Medicine, the standard medical bible at the time, stated i
Between 1958 and 1986, the number of children aged 4 or younger admitted to hospital increased 20-fold from four per 10,000 to 80 per 10,000 (BMJ, 1990; 100: 1306-10). There has been another major increase in this rate since 1986.
Why should this be? Many observers put it down to increasing outdoor air pollution, particularly nitric oxide emissions from cars. But this does not explain why the least polluted part of the UK, the island of Skye, has a higher incidence of asthma, at 17 per cent, than Aberdeen or Cardiff, which both had around 11 per cent (Archives of Diseases in Childhood, 1994; 71: 211-16). Similarly, Leipzig in former East Germany, which has severe pollution, had a lower asthma rate just after the fall of the Berlin wall than Munich, which is far less polluted (Am J Respir Crit Care Med, 1994; 149: 358-64). At most, pollution is thought to cause just 5 per cent of asthma attacks.
So what is the real cause of this increase? My conclusions, from years of research and observation of patients, is that there are three main factors:
A vast increase in indoor air pollution;
Repetitive diets, with too much wheat, sugar, dairy products, soy and yeast, which lead to a high incidence of food sensitivity;
Over-reliance on drug suppression for asthma treatment (see WDDTY Guide to Asthma & Eczema).
The prime function of the immune system is to distinguish between invaders which may be harmful microbes which cause disease from those which are harmless pollen, dust and dustmites, and food molecules. The ability to make this distinction and not to react to harmless items is called tolerance induction. Animal studies show that inhaling certain chemicals can interfere with this process and stop animals' immune systems learning tolerance to harmless substances.
One of the main chemical culprits is nitrogen dioxide, which is not only present in car fumes, but is spewed out from gas cookers and gas and oil boilers. Modern homes are also riddled with other chemicals: formaldehyde, trichlorethelene, phenol, for example, are used in things like carpets, chipboard and soft plastics. Most of us now have well insulated homes, which means these substances are unable to disperse.
We don't know for sure that what happens in animals necessarily translates across into humans, but there are parallels in this instance. An American study published in the Lancet found that gas cookers generated concentrations of nitrogen dioxide of 200-400 parts per billion levels which would only be found outside during severe bouts of air pollution. Further, a study of children aged 3-4 found a striking association between exposure to nitrogen dioxide and asthma (Am J of Epidemiology, 1993; 137: 834-44).
It, therefore, seems that the growth in what is called "extrinsic" asthma asthma linked with a history of dust, dustmite and mould sensitivity, backed up by positive pin prick tests may be explained by the combination of indoor chemicals, inhaled allergens like dust and dustmites, and hermetically sealed homes.
The other form of the condition, so-called "intrinsic" asthma, is often but not always linked with food sensitivity. A high proportion of patients diagnosed with intrinsic asthma will find their symptoms disappear if they go through a standard elimination diet to find out what foods they are reacting to. These will often be the common allergens for example wheat, sugar, milk products although any food can be implicated. There are several published studies of hundreds of patients that show that food sensitivity is a major cause of asthma evidence that has been largely ignored by the medical establishment, which prefers to carry on dishing out drugs to suppress the symptoms rather than eliminate the cause (J Brostoff, Food Allergy and Intolerance, Balliere Tindall, 1987).
The fact that asthma may be caused more by indoor, rather than outdoor, pollution is actually good news for sufferers. There isn't much that we, as individuals, can do directly to influence out outdoor environment. Even with the fitting of catalytic converters, it is unlikely that a major change will occur in external pollution levels within the next 20 years. However, our indoor air environment and the food we eat are factors which are generally within our individual immediate control.
Dr John Mansfield is a leading allergy specialist. His latest book, Asthma Epidemic (Thorsons, 1997), explores these issues in greater detail.