Frequency of infections, atopic eczema and asthma outcome in infancy

Abstract

Frequency of infection per year since birth in relation to the development of asthma by 2 /2 to 3 /2 years of age produced a bell shaped curve with both very low and very high frequencies of infections being associated with less asthma. It has recently been estimated that the mean annual number of infections per year in infancy up to two years of age is 3.4 and in the pre-school age children 2.3. However in infancy up to 11 infections per year have been reported as being within the normal range based on the two fold standard deviation from the mean (3). Thus all the reported frequencies in this study would be considered to be within the normal range but nevertheless are associated with significant differences in outcomes in relation to asthma. Very low frequency of infection may be a surrogate marker of an infant with a highly effective TH-1 response which will be associated with a reduced probability of allergic disease evolving into asthma while those with very high frequency of infection have a greater probability of inducing TH-1 responsiveness and thereby reducing the allergic drive. Normal rates of infection in atopically predisposed individuals will not modify outcome. These data may perhaps go so some way to explain the discrepancies found in many other studies investigating these associations where actual frequency of infection has not been assessed. DISCUSSION INTRODUCTION