The PIAMA study (Prevention and Incidence of Asthma and Mite Allergy) is a combination of an intervention trial and a natural history study of the development of asthma and allergic disease in childhood. The aims of the study are
1) to investigate the effect of mite allergen avoidance on the incidence of asthma in childhood (Intervention Study) and
2) to investigate the incidence of asthma in children from 0-8 years (Natural History Study). The study has been ongoing since 1996.
The intervention study takes place in children born to allergic mothers (high risk children). The intervention that is being evaluated is application, from birth, of mite allergen impermeable mattress covers on baby beds; subsequently, on mattresses and pillows when the study children move into a larger bed; and on mattresses and pillows of the parental bed. The placebo treatment is application of cotton, mite allergen permeable covers. The intervention measure was chosen on the basis of earlier Dutch studies showing high mite allergen loads on mattresses, suggesting that encasement of mattresses would remove an important source of mite allergens in the immediate surroundings of the child; it was chosen because of its ease of application, making it a measure likely to be relatively easy to implement if proven effective; it was chosen because it is one of the few measures which can be studied in a randomised, double-blind placebo controlled trial; and, finally because previous studies had suggested that mattress encasement dramatically reduced mite allergen exposure, and were beneficial to mite-allergic patients.
The natural history study takes place among children born to allergic mothers (high risk) as well as non-allergic mothers (low-risk children). The natural history study follows a large group of children from birth to study the development of asthma and allergic disease over time, in relation to a environmental and lifestyle factors that may increase or reduce the incidence of asthma and allergic disease. These include breast feeding, maternal and child dietary habits, exposure to allergens from mites, cats and dogs, exposure to bacterial endotoxin and mould components, to environmental tobacco smoke, to gas cooking fumes, and to traffic-related outdoor air pollutants. In addition, information is being collected on allergic disease in family members, day care usage, family size, childhood respiratory infections, vaccinations, use of antibiotics and other medications, and a variety of other lifestyle issues. The high risk children in the natural history study also provide a second control group for the intervention study to study the presence of a placebo effect.
The PIAMA children will become 8 years old in the period summer 2004 - fall 2005. At 8 years, reliable diagnosis of allergic disease (asthma, rhinitis, eczema) is possible using, for the first time in this cohort, a range of techniques including serum IgE, skin prick tests and tests of bronchial reactivity. Detailed clinical investigation of as many study children as possible will provide the data that are needed to obtain the returns on the investments made in the study so far.
For reasons explained in more detail in the proposal, the intervention measures that were applied resulted in less allergen reduction than anticipated. We do not foresee, therefore, that there will be large differences in asthma and (other) allergic manifestations between the study groups at age 8. Yet, it cannot be excluded that even modest reductions in exposure during the presumed period of increased vulnerability early in life may have long-term consequences for the development of asthma and (other) allergic diseases. Detailed clinical assessment of the children in the intervention study will provide the answer to this question.
In the last ten years, there has been a stormy development of ideas and hypotheses to explain the increase in allergy and asthma in childhood. These include the role of early life exposure to infectious agents ('hygiene hypothesis') and the role of western lifestyle more in general including aspects of nutrition and medical care. Long-term, prospective studies such as PIAMA are needed to address the various hypotheses that have been formulated; among all prospective birth cohort studies currently being conducted in the world, the PIAMA study ranks among the largest; it is also a study that has invested heavily in detailed assessment of a range of environmental and lifestyle exposures, including allergens, bacterial endotoxins, mould components in the house, nutrition, outdoor air pollution etc. The study has already proven to provide important new information on the role of a range of risk factors which are in large part modifiable, and hence suitable for development of new preventive strategies.