[Environmental influences in asthma].
Beside genetic factors environmental factors largely determine prevalence and severity of bronchial asthma. They seem to explain better the large time-related and geographic differences in prevalence, supported by several recent studies. Among environmental risk factors, those present indoors, linked to our modern homes, are considered most important. This applies to early exposure to allergens, especially to house dust mite, first leading to sensitisation and later to asthma. The indoor air may also be contaminated by tobacco smoke and other substances like nitric oxide, acting directly on the airways or indirectly by promoting sensitisation to allergens. Atmospheric air pollution is the environmental factor mostly considered as responsible for the asthma increase. Its role as inducer of the disease has not been established, but cannot be excluded. New and known agents of air pollution in the working place have resulted in asthma becoming the most frequent occupational respiratory disease. Respiratory infections have long been considered as a risk factor for asthma, e.g. those caused by RSV-viruses; however, recent evidence suggests that infections during the first year of life could be protective for asthma. Changed dietary habits are a possible risk factor linked to our altered life style. Current research evaluates the role of excessive salt intake, or deficient intake of fruit and omega-3 fatty acids from fish oil. There is growing evidence that risk factors for later occurrence of asthma could already act very soon after birth or even during pregnancy; this would apply for exposure to parental smoking or to allergens. Although aggravating environmental factors undoubtedly have an important role in the pathogenesis of asthma, it remains an intriguing question to what extent the loss of protective mechanisms resulting from our Western life style is not the main cause of the increased occurrence of asthma. Better understanding of this problem is mandatory and urgent for rapidly instituting effective prevention.
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Afdeling Pneumologie-Depart. Geneeskunde Universiteit Antwerpen (UIA).
D000397:Air Pollution; D016902:Air Pollution, Indoor; D001249:Asthma / Q000453:epidemiology / Q000209:etiology*; D004787:Environmental Pollution; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011248:Pregnancy Complications; D015995:Prevalence; D012141:Respiratory Tract Infections / Q000453:epidemiology; D012307:Risk Factors