Breastfeeding and Risk of Rheumatoid Arthritis: A Systematic Review and Metaanalysis.

OBJECTIVE Previous studies have examined the association between breastfeeding and rheumatoid arthritis (RA), but their results were inconsistent. The aim of this study was to perform a metaanalysis to clarify the effect of breastfeeding on RA risk. METHODS The PubMed, EMBASE, Chinese National Knowledge Infrastructure, and Wanfang databases were searched for relevant studies published up to September 10, 2014. Data were extracted, and multivariable-adjusted OR with 95% CI were pooled in the random-effects model. RESULTS A total of 6 studies were included in the metaanalysis (RA cases: 1672, sample size: 143,670). Overall, an inverse association between breastfeeding and RA was observed (OR 0.675, 95% CI 0.493-0.924, p = 0.014). In the subgroup analysis, decreased RA risk was also found in both breastfeeding 1-12 months (OR 0.783, 95% CI 0.641-0.957, p = 0.015) and breastfeeding > 12 months (OR 0.579, 95% CI 0.462-0.726, p < 0.0005). Sensitivity analysis and cumulative analysis further strengthened the validity of the results. No publication bias was found in this metaanalysis. CONCLUSION This metaanalysis suggests that breastfeeding is associated with a lower risk of RA, no matter if breastfeeding time is longer or shorter than 12 months.