Antibiotics in the first week of life were associated with atopic asthma at 12 years of age

AIM: This study explored the prevalence of atopic and nonatopic asthma in 12‐year‐old children and whether they were associated with different risk factors. In particular, we wanted to analyse whether receiving antibiotics during the first week of life was associated with asthma at that age. METHODS: Data were obtained from a longitudinal cohort study of 5654 Swedish children born in 2003. The parents answered questionnaires from the age of six months until 12 years. The response rate at 12 years was 3637/4777 (76%). RESULTS: At 12 years, 6.4% reported current doctor‐diagnosed asthma. Treatment with antibiotics during the first week of life was associated with an increased risk of atopic asthma, with an adjusted odds ratio of 2.2 and 95% confidence interval of 1.2–4.2. Being born small for gestational age was associated with an increased risk of nonatopic asthma, with an adjusted odds ratio of 3.8 and 95% confidence interval of 1.1–13.7. Asthma that only occurred with colds was reported by 28%. CONCLUSION: Antibiotic treatment during the first week of life was associated with an increased risk of atopic asthma at 12 years, suggesting an immune‐mediated effect. Being born small for gestational age increased the risk of nonatopic asthma.