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 ⩽1 episode of runny nose before the age of 1 year, those with ⩾2 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 ⩾1 viral infection of the herpes type in the first 3 years of life was inversely associated with 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 ⩾4 infections v ⩽3 infections). CONCLUSION: Repeated viral infections other than lower respiratory tract infections early in life may reduce the risk of developing asthma up to school age.