Introduction of fish and other foods during infancy and risk of asthma in the All Babies In Southeast Sweden cohort study.

The etiology of asthma includes lifestyle factors. Breastfeeding and introduction of complementary foods have been suggested to affect asthma risk, but the scientific foundation is not solid. Children from the birth cohort All Babies In Southeast Sweden study were included (n = 9727). Breastfeeding duration and timing of introduction of infant formula and food were collected prospectively during the first year. Through linkage to the Swedish Patient Register, 948 children were identified with any asthma until age 15-17 years, of which 450 cases were atopic. Breastfeeding duration was not associated to risk of asthma. Introduction of infant formula earlier than at 14 weeks of age was associated with higher risk of non-atopic asthma. Introduction of fish before 43 weeks of age, as compared to later, was associated with a lower risk of asthma, irrespective of atopic classification. Reverse causation was accounted for but did not explain the results.Conclusion: Introduction of infant formula and timing of introduction of fish seem to impact the long-term risk of doctor-diagnosed asthma. Emphasis on the growing body of evidence that early introduction of allergens offers protection against atopic disease should be considered in future recommendations. What is Known: • Breastfeeding and introduction of complementary foods might influence the risk of atopic diseases. Recently, a review stated that more studies are needed to clarify the role for asthma development. What is New: • Introduction of infant formula earlier than at 14 weeks of age was associated with a higher risk of developing non-atopic asthma. The risk was pronounced in children introduced to infant formula before 4 weeks of age while being breastfed less than 4 weeks. • Early fish introduction, before 43 weeks of age, was associated with a lower risk of asthma, independent of atopic classification of asthma.