Excerpt
Pages 78 - 85 The asthma epidemic--and how to beat it '. . . we thought we had made a mistake . . .' When researchers in Germany decided to look at the number of children with asthma, and compared the numbers in a West German city with numbers in two highly polluted cities in East Germany, they expected to find more asthma in the East. They did find more coughing and wheezing in the East, but when it came to asthma, the results were exactly the opposite. Initially the researchers reacted with disbelief. 'We checked all the data entries again because we thought that we had made a mistake,' said the research team leader, Dr Erika von Mutius of the University Children's Hospital in Munich. The children in West Germany had far more allergies than those in the East, and therefore more asthma, despite breathing cleaner air. WHY IS ASTHMA ON THE INCREASE? There is no doubt now that asthma truly is on the increase. At one time it seemed possible that doctors had just become more inclined to diagnose asthma, rather than, say, 'wheezy bronchitis' or 'a cough', producing an artificial increase in the asthma statistics. New research shows that, although this diagnostic shift has happened, there is also a genuine and sizeable increase in the number of asthma sufferers. Between 1975 and 1995, asthma rates in children doubled in many parts of the world, and the rates for adults also rose sharply. It is no exaggeration to call this an epidemic. A Western epidemic The asthma epidemic is affecting all the rich, Westernized countries of the world. It is also affecting immigrants to Western countries arriving from places where asthma is rare.For example, when people from the Polynesian island of Tokelau move to New Zealand, their chances of getting asthma double. Similar increases have been seen among Filipinos moving to the USA, and Asians from East Africa moving to Britain. The new cases of asthma occur among adult immigrants, as well as their children. For black South Africans moving to Cape Town, rates of asthma in the next generation are 20 times higher than in the rural villages where the people originated. Chinese people in Taiwan, who have stayed in the same place but gradually adopted a Westernized lifestyle, now have eight times more cases of childhood asthma than they had in 1974. In Ghana, the wealthier people living in the cities are also experiencing more and more asthma, whereas the poor people living in the same cities have far less asthma, and people in the remote villages have little or none. Research has revealed the same thing in Zimbabwe. All these communities have also experienced rising levels of other allergic diseases. Looking at all this research, it is obvious that the asthma epidemic is being caused by some factor or factors in modern Westernized life. Whatever the factors are, they seem to have appeared in the early 1960s and they affect rich and poor alike in Britain and other Western countries, but failed to affect people in East Germany before German unification. Another puzzling fact about the worldwide distribution of asthma is that rates seem to be very high in parts of Latin America, particularly Brazil and Peru, and not just among the wealthier classes. What is causing the epidemic? Air pollution is usually blamed, but the case against air pollution just doesn't stand up. Although it can make asthma worse for people who already have the disease, and it may produce a small increase in the number of people developing asthma, there is no way that air pollution is the major cause of the asthma epidemic. Some places with extremely clean air, such as New Zealand, have very high rates of asthma (see pp. 205-6). The poor urban children in Ghana (see above) are breathing the same polluted air as the rich urban children, but suffer much less from asthma. So what is the cause? There is no simple answer to this question, but many different factors have been identified. Some of these are universal in Westernized countries and communities, others are not. It looks as if the factors in question vary from one country to another, from one region to another, and even from one asthmatic to another. So some of the factors listed below may be relevant to you and your family, and some may not. Bear in mind that all these factors will probably make no difference to a person who does not have the inborn tendency to develop allergies and/or asthma (see p. 25). It is primarily those with the inherited susceptibility to asthma who will be affected by these changes in lifestyle. It is interesting that the large differences between East and West Germany (see p. 78) only occurred in the generations born after 1961: before that, West Germans had as little asthma as those in the East. The same is true when people in Sweden are compared with those in Estonia. As one researcher points out, 'Living conditions in the formerly socialist countries of Europe are, in many respects, similar to those that prevailed in Western Europe 30-40 years ago, including the type of air pollution, the panorama of childhood infections, types of immunizations, building standards, and food.' Looking at the worldwide picture, there is a general link between asthma and affluence, but within developed countries such as Britain, asthma rates are the same in all social classes. In other words, the risk factors are shared by rich and poor alike in the West. This would fit in with risk factors such as a high-salt diet (for example from crisps and other salty snacks), sedentary indoor lifestyle, altered patterns of childhood infections due to sanitation and medical care, and poorly ventilated housing leading to allergen build-up. Such factors are shared by rich and poor alike in developed countries, but are still rare in rural Africa and Asia where asthma rates remain very low. These are some of the likely causes of the asthma epidemic: A change in diet: A high intake of salt, and relatively few fresh fruits or vegetables, may make people more likely to develop asthma. Diets rich in fat, especially saturated fat, and low in important minerals such as selenium and zinc, could also increase the risk (see pp. 96-104). One of the problems with such a diet is that it tends to promote inflammation. The diet that women eat when pregnant may also affect the baby's chance of developing allergies, but this is not well understood yet (see p. 28). Less ventilation and more heating: All those tightly fitting windows and money-saving draught excluders have reduced the air-flow through our houses, so that allergens, which are one cause of asthma (see p. 110), can build up to very high levels in the air. With less ventilation there is also more condensation and damp, which encourages mould growth (see p. 117). Warmth and damp are also ideal for house dust mites, one of the most common causes of asthma (see p. 115). More fitted carpets and upholstered furniture: Given poor ventilation and greater humidity (see above), fitted carpets increase the levels of house dust mite allergens in our homes. Thick curtains (drapes), and sofas and armchairs covered with fabric rather than leather also contribute to the problem. House dust mites live in carpets and soft furnishings in their millions. You cannot see them because they are extremely small, but they are there. Old-fashioned homes, with wooden floors, a few rugs, rattling windowpanes and ferocious draughts, harboured far fewer mites (see p. 147). Changes in washing temperatures: Clothes, bedding and furniture covers are now washed at much lower temperatures. The introduction of detergents that wash at lower temperatures was good news for house dust mites as they are only killed by temperatures of 55 degrees C (131 degrees F) and above (see p. 131). Soft toys: Children have more soft toys, and they often sleep with their faces snuggled up against them, inhaling all the allergens from the millions of house dust mites living happily in the toys (see p. 137). Pets: More dogs, cats and other furry pets are now kept and they are more likely to live in the house rather than outside, often sleeping on their owners' beds. If children are exposed to pets during their first year of life they are much more likely to become allergic to them, and this increases the risk of asthma later, when they are two years old or more (see p. 29). All pets, apart from fish, can provoke allergies and asthma (and some people become allergic to the ants' eggs used for fish food). Moulds and cockroaches: In run-down housing, there are more moulds and, in warmer climates, cockroaches. Being exposed to airborne allergens from moulds or cockroaches during the first year of life raises the risk of asthma developing in children (see p. 26). Allergy to cockroaches probably explains the very high levels of asthma in American inner-city areas. More time spent indoors: Most of us now spend much more time indoors than out, and children, in particular, spend far less time playing outside than they did in the past. A child slumped on a sofa watching a video or playing a computer game is breathing very shallowly, as well as inhaling large quantities of indoor allergens, especially dust mites. Children running around outside are not only breathing better air, they are also exercising their lungs which increases the capacity and elasticity of the airways and therefore helps protect against asthma (see p. 68). Changing patterns of indoor pollution: Breathing high concentrations of nitrogen dioxide gas from gas cookers and gas fires, in combination with high levels of allergen, increases the risk of asthma in young children (see pp. 207-8). Old-style indoor pollution, on the other hand, may have protected against asthma. Studies from Britain, Germany and Australia all show that using coal or wood to heat the house may reduce the risk of asthma. This could be due to increased ventilation reducing house dust mite numbers, but some think that the smoke itself might, indirectly, reduce the risk of asthma (see pp. 211-2). Cigarette smoking: More women now smoke, and many continue smoking during pregnancy and afterwards. Babies born to smoking mothers are more likely to develop asthma, and allergies in general (see p. 89). Other adults smoking in the house after the baby is born may also increase the risk of asthma. A change in the pattern of childhood illnesses: Several different lines of evidence link increased rates of allergy and asthma with smaller families and more hygienic conditions. A study in East Germany found that children living in overcrowded conditions were much more likely to have had parasitic infections, and much less likely to have allergies. Overcrowding in Estonia and Poland is also associated with lower levels of allergy and asthma. Parasitic worm infections seem to protect against allergy (see p. 27). Other research shows that children who wash more run a higher risk of asthma (see p. 93) and in this case infection with harmless soil-living bacteria may be responsible (see p. 27). One African study suggests that measles infection protects against the development of dust-mite allergy, but measles vaccination does not. On the other hand, some common viral infections causing chest infections in young children may promote allergic reactions (see p. 93), and these viral infections are probably more common today. Frequent courses of antibiotics during childhood: Antibiotics, if given to babies under two years of age, increase the risk of asthma (see pp. 92-3). More sexually transmitted infections: One particular infection of the urinary and genital tract can be transmitted from the mother to the baby during birth, and the child is then three or four times more likely to develop asthma in later life (see p. 88). The bacterium may cause no obvious symptoms in the mother. About 50 per cent of Western women are carrying this bacterium, and most are unaware of it. Levels of infection were probably lower 40 or 50 years ago. More traffic pollution: Some types of traffic pollution may very slightly increase the risk of allergies and/or asthma developing in children (see pp. 207-11). Note that this effect might boost the number of asthma sufferers a little, but, taken alone, it cannot account for the vast scale of the epidemic. Exposure to pesticides: A study in Ethiopia showed that use of one insecticide almost doubled the risk of allergy while research in Canada has linked asthma with carbamate insecticides (see p. 223). Exposure to other chemicals: There is a small piece of indirect evidence on this point: a Canadian study showed that children living in newer houses were more likely to develop asthma (see p. 225). Other theories about the asthma epidemic - true or false? Are house dust mites alone causing the epidemic? There are people, including some experts in this field, who seem to be claiming that house dust mites are the major, if not the sole, cause of the current asthma epidemic. Don't you believe it! A study in Los Alamos, New Mexico, a high-altitude region where there are virtually no dust mites, found that rates of asthma were just as high as elsewhere in the USA. Studies in the former East Germany found that people had high levels of dust mite infestation in their houses, yet relatively low rates of allergy to dust mites, before German unification when the standard of living was low. People in West Germany, with a far more affluent Western lifestyle, had fewer house dust mites, but they were more likely to become allergic to them. What about vaccinations? You may have heard that vaccinations, particularly for whooping cough, increase the risk of asthma developing later in childhood. The evidence on this is conflicting (see pp. 94-5), suggesting that vaccina- tions only make a difference if certain other factors are present or absent. Could car travel cause asthma? A doctor in Tasmania has suggested that, for unborn babies, the rise in stress hormones that occurs when their mothers travel by car increases the risk of asthma after the child is born. His evidence is simply that rates of asthma in Australian children have increased roughly in line with the time women spend travelling by car. No one has taken this theory seriously, so it has never been tested. Many other changes in society have occurred at the same time as increasing car travel. Slightly more impressive evidence comes from Ethiopia, where, in one small country town, adults who owned a car had four times the risk of becoming allergic to house dust mites (and dust-mite allergy increased the risk of asthma ten times). But this link could be explained in many other ways. Those with a car were a tiny minority, and were probably more Westernized than their neighbours in a great many other ways as well. 'Before 1930, carpets were never left down, and they were regularly beaten.' Professor Tom Platts-Mills is an allergist working at the Uni- versity of Virginia in the USA. 'Before 1930, carpets were never left down, and they were regularly beaten. Carpets were unusual in housing of low-income families, and they were put in storage from May to October in middle- or upper-class houses. Thus Edith Wharton wrote in 1905 in The House of Mirth that Mrs Peniston was "as much aghast as if she had been accused of leaving her carpets down all summer or of disobeying one of the equally cardinal rules of good housekeeping". After 1930, the vacuum cleaner was introduced. Vacuum cleaner sales people, then and now, convinced the public that carpets can be cleaned while on the floor, which is only partly true . . . Allergists have attempted to keep up with the pace of change in the outside world and in housing . . . In the next ten years, the objective of doctors who treat patients with allergic diseases should be active involvement in the design of houses, in their flooring, heating, ventilation and furniture.' 'We have been losing the war against smoking in young women . . .' There are many factors involved in causing the current asthma epidemic in Western countries. 'We have actually been losing the war against smoking in young women of child-bearing age,' says Dr Kenneth Chapman, director of the Asthma Centre at the Toronto Hospital. 'We put together infants living in nice, warm, humid, insulated homes with pets and dust mites and a few more mothers who smoke, and we have the stage set for sensitizing young airways.'