Contributing factors to the development of childhood asthma: working toward risk minimization

Abstract

Asthma is the most common chronic disease in childhood, and considerable research has been undertaken to find ways to prevent its development and reduce its prevalence. For such interventions to be successful, risk factors for asthma emergence should be identified and clearly defined. Data are robust for some of them, including atopy, viral infections and exposure to airborne irritants, whereas it is less conclusive for others, such as aeroallergen exposure and bacterial infections. Several interventions for asthma prevention, including avoidance and pharmacotherapy, have been attempted. However, most of them have furnished equivocal results. Various issues hinder the establishment of risk factors for asthma development and reduce the effectiveness of interventions, including the complexity of the disease and the fluidity of the developing systems in childhood. In this review, we revisit the evidence on pediatric asthma risk factors and prevention and discuss issues that perplex this field.

Keywords:

• asthma
• avoidance
• interventions
• pharmacotherapy
• prevention
• risk factors

Financial & competing interests disclosure

NG Papadopoulos has received research support for his institution by Nestle, MSD and GSK; has acted as a consultant for Abbvie, Novartis, Menarini, Meda, ALK-Abello, GSK; has received honoraria from Novartis, Uriach, GSK, Allergopharma, Stallergenes, MSD; and has been on the scientific advisory board for Abbvie, Sanofi, Menarini, Meda. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Genetic susceptibility is an important underlying factor of asthma development. However, it is unlikely to account for the rapid rise in asthma prevalence that has taken place in the past decades. Environmental exposures are likely to be the key culprit.

• Atopy is a clear-cut risk factor for asthma development. However, the actual exposure to allergens is not conclusively shown to be a risk factor in its own right. Allergen avoidance interventions are generally ineffective for asthma prevention.

• Early viral infections, especially with respiratory syncytial virus and RV, are a well-recognized risk factor. However, the effect of microbes, both indigenous and environmental, and the modification of this effect by their pathogenicity and diversity is unclear. Such microbial exposures may in fact be protective, as suggested by the hygiene hypothesis and currently extended by the superorganism and biodiversity concepts.

• Exposure to airborne pollutants and second-hand smoke is a well-documented risk factor for asthma development and should be avoided.

• Data are not conclusive, albeit is mostly supportive for other risk factors, including obesity and stress and for other interventions including breastfeeding.

• Pharmaceutical interventions are generally ineffective. Specific immunotherapy is the most promising one, but its effectiveness remains to be confirmed.

• Research on risk factors for asthma development is laborious due to the complexity of the disease, the limitations of the study design, and the fluidity of the immune and respiratory systems during childhood.