Table 1

Some postulated factors associated with two common types of wheezing syndrome, at different ages

Risk or causal factorTypical period in childhoodTypical example*Comment
Early (0-3 years)Later (> 5 years)
Disturbance in lung growth+BMaternal smoking implicated6 7
Increased susceptibility to respiratory virus infections+++B>ABreastfeeding protective8 Possibly related to
  environmental pollution9 10 Associated with low birth weight11
Excessive airway secretions++±B>A
Acute airway inflammation
  (A) Virus+++A and B 12
  (B) Allergen±++A
Chronic airway inflammation?++A 13 14
Smooth muscle constriction (β2responsiveness)+++A>BPossibly different pathways at different ages
Bronchial responsivenessUnrelated to
  symptoms or atopy (B)7 15-17
Related to
  symptoms and atopy (A)4 18-20
A and BFamilial element present in both types20 22
  • Environmental and host factors will determine actual age and period over which these factors operate. The ‘asthma’ phenotype is dependent on the precise combination of factors present in an individual.

  • Key: * syndromes A and B are described in the text and are meant only to represent possible varieties of wheezing disease, and not to suggest that these are the only varieties or that they are necessarily mutually exclusive.