Breastfeeding and risk of childhood asthma: a systematic review and meta-analysis

OBJECTIVE: To investigate the relationship between breastfeeding and the development of paediatric asthma. METHODS: A systematic review and meta-analysis was conducted with MEDLINE, Embase, CINAHL and ProQuest Nursing and Allied Health source databases. Retrospective/prospective cohorts in children aged <18 years with breastfeeding exposure reported were included. The primary outcome was a diagnosis of asthma by a physician or using a guideline-based criterion. A secondary outcome was asthma severity. RESULTS: 42 studies met inclusion criteria. 37 studies reported the primary outcome of physician-/guideline-diagnosed asthma, and five studies reported effects on asthma severity. Children with longer duration/more breastfeeding compared to shorter duration/less breastfeeding have a lower risk of asthma (OR 0.84, 95% CI 0.75–0.93; I(2) = 62.4%). Similarly, a lower risk of asthma was found in children who had more exclusive breastfeeding versus less exclusive breastfeeding (OR 0.81, 95% CI 0.72–0.91; I(2)=44%). Further stratified analysis of different age groups demonstrated a lower risk of asthma in the 0–2-years age group (OR 0.73, 95% CI 0.63–0.83) and the 3–6-years age group (OR 0.69, 95% CI 0.55–0.87); there was no statistically significant effect on the ≥7-years age group. CONCLUSION: The findings suggest that the duration and exclusivity of breastfeeding are associated with a lower risk of asthma in children aged <7 years.