Early childhood infectious diseases and the development of asthma up to school age: a birth cohort study

Objective To investigate the association between early childhood infections and subsequent development of asthma. Design Longitudinal birth cohort study. Setting Five children's hospitals in five German cities. Participants 1314 children born in 1990 followed from birth to the age of 7 years. Main outcome measures Asthma and asthmatic symptoms assessed longitudinally by parental questionnaires; atopic sensitisation assessed longitudinally b y determination of IgE, concentrations to various allergens; bronchial hype rreactivity assessed by bronchial histamine challenge at age 7 years. Results Compared with children with less than or equal to1 episode of runny nose before the age of 1 year, those with greater than or equal to2 episod es were less likely to have a doctor's diagnosis of asthma at 7 years old ( odds ratio 0.52 (95% confidence interval 0.29 to 0.92)) or to have wheeze a t 7 years old (0.60 (0.38 to 0.94)), and were less likely to be atopic befo re the age of 5 years. Similarly, having greater than or equal to1 viral in fection of the herpes type in the first 3 years of life was inversely assoc iated wit asthma at age 7 (odds ratio 0.48 (0.26 to 0.89)). Repeated lower respiratory tract infections in the first 3 years of life showed a positive association with wheeze up to the age of 7 years (odds ratio 3.37 (1.92 to 5.92) for greater than or equal to4 infections v less than or equal to3 in fections). Conclusions Repeated viral infections other than lower respiratory tract in fections early in life may reduce the risk of developing asthma up to schoo l age.