Primary Prevention Of Asthma

The relentless increase in the prevalence of asthma and allergic diseases highlights the need for devising effective preventive strategies. Although the genetics of these disorders are being investigated, manipulation of known environmental risk factors remains the best available approach to this problem. However, the large number of potential environmental risk factors and our inability to accurately predict the development of asthma and allergy has led to conflicting data from recent prevention studies.

Nonetheless, some useful recommendations can be made. Exclusive breast-feeding and avoidance of exposure to environmental tobacco smoke exposure can be safely recommended for the whole population, not only for prevention of allergy but also for other known benefits. Additionally, for children at high risk of allergy, maternal exclusion diet during lactation and protein hydrolysate as a supplement or alternative for children who could not be breast-fed seems to provide further protection.

The preventive effect of avoidance of house dust mite allergen alone during pregnancy or after birth is disappointing. However, prospective randomized studies evaluating a combined food and house dust mite allergen avoidance regimen show some protection against atopic dermatitis in infancy and asthma in later childhood. Urgent research is needed to accurately identify children at high risk and to test novel preventative measures with the potential for immunomodulation.

Further randomized controlled trials are also needed with long-term follow up to evaluate combined approaches that might provide maximum benefit. Asthma is one of the commonest chronic diseases worldwide and is increasing in children and probably also in adults. While it is a worldwide problem, the prevalence of the condition seems to be higher in affluent than nonaffluent populations. The prevalence of childhood asthma has been reported to vary between 1% and 30% in different populations.

One of the major problems associated with tracking trends with time and trends between countries relates to different definitions of asthma being used. When the same test is used in the same place at different times, it can be seen that in south Wales, for example, the prevalence of childhood asthma increased from 11% to 15% over a 15year period. In Australia, the prevalence of reported wheezing in the previous 12 months doubled from 12% to 24% in schoolchildren between the years 1980 and 1990.

In the United Kingdom, latest figures suggest a childhood asthma prevalence of 13% of the population and an adult rate of between 5% and 8%. With conflicting data on early life exposure to pets, no general recommendation can be made with regard to avoiding pets for primary prevention of allergy and asthma (level III). However, families with biparentalatopy should avoid having cats or dogs in the home (level II).

There are conflicting and insufficient data for physicians to recommend for or against breastfeeding specifically for the prevention of asthma (level III). Due to its numerous other benefits, breastfeeding should be recommended. It has been assumed that breastfeeding is preventative against early childhood wheezing and the subsequent development of asthma and that exposure to pets is a risk factor for the development of asthma. Recent studies have brought these general assumptions into dispute, and we considered the available data addressing these 2 important issues.