Understanding the relationship between breastfeeding and childhood asthma: A systematic review and meta-analysis

Background: Despite breastfeeding being widely recommended, its relationship with asthma continues to be debated. Aims: To carry out a systematic review and meta-analysis of cohort studies to understand if breastfeeding (BF) is inversely associated with physician diagnosed asthma in children. Methods: A comprehensive search was conducted on cohort studies published until June 2018 in any of MEDLINE, EMBASE, Cochrane, CINAHL and ProQuest Nursing and Allied Health Source databases. A manual search of references was conducted for additional resources. Data extraction were restricted to cohort studies or randomized controlled trials that reported physician diagnosed asthma in children aged <18 years old and had BF as an exposure. Full screening of 173 articles was carried out from the initial search results of 2599 articles that underwent title and abstracts screen. Risk of bias was assessed using a modified Newcastle Ottawa Score for cohort studies and random effect was used to calculate the pooled effect estimate. Results: Out of 46 articles, the meta-analysis of 26 studies indicated that BF compared to no BF was associated with a 21% lower risk of asthma (Pooled effect size, 95% CI=0.79, 0.76-0.83) on asthma and BF. Similarly, children who had been exclusively BF had 28% lower risk (0.72, 0.64-0.80) of asthma and those who had partially breastfed had 17% lower risk (0.83, 0.76-0.90). The heterogeneity among studies that reported any, exclusive and partial BF were 46%, 30% and 45% respectively. Conclusions: The findings suggests that there is 17 to 28% lower risk of asthma in children who are breastfed more, strongly supporting the advocacy for breastfeeding.