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 by determination of IgE, concentrations to various allergens; bronchial hyperreactivity 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 episodes 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 at 7 years old (0.60 (0.38 to 0.94)), and were less likely to be atopic before the age of 5 years. Similarly, having greater than or equal to1 viral infection of the herpes type in the first 3 years of life was inversely associated 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 infections). Conclusions Repeated viral infections other than lower respiratory tract infections early in life may reduce the risk of developing asthma up to school age.