Supplementary Material for: Breastfeeding and Atopic Dermatitis Risk: A Systematic Review and Meta-Analysis of Prospective Cohort Studies

Objectives: The effect of breastfeeding on atopic dermatitis (AD) remains controversial. To determine the association ­between breastfeeding and AD, we conducted an updated meta-analysis of prospective cohort studies. Methods: A comprehensive search of PubMed, EMBASE, MEDLINE and Cochrane Library was conducted. Studies meeting the predetermined criteria were evaluated by 2 authors independently. The pooled relative risk (RR) adjusted for confounders with its 95% CI was calculated by a random-effects model. Heterogeneity was explored by subgroup analysis and meta-regression. Results: A total of 27 studies were included for meta-analysis. The pooled estimates for the effect of total and exclusive breastfeeding on AD were 1.01 (95% CI 0.93–1.10) and 0.99 (95% CI 0.88–1.11), respectively. Heterogeneity was substantial across studies (total: p < 0.01 or I² = 65.2%; exclusive: p < 0.01 or I² = 72.3%). There was a weak evidence for a protective effect of breastfeeding against AD in cohorts with atopic heredity (total: RR 0.85, 95% CI 0.74–0.98; exclusive: RR 0.83, 95% CI 0.70–0.97). In cohorts without atopic heredity, the effect shifted to the risk side when limited to exclusive breastfeeding (RR 1.19, 95% CI 1.02–1.40) while it dropped towards null when limited to total breastfeeding (RR 1.11, 95% CI 0.94–1.31). Conclusions: There is no association between AD and breastfeeding, regardless of total or exclusive breastfeeding patterns. There is some evidence for a protective function of exclusive and total breastfeeding in a cohort with atopic heredity. The effect shifts to the risk side in cohorts without atopic heredity. However, these findings should be interpreted with caution because heterogeneity is evident.