The Effect of Breastfeeding Duration on Bone Mineral Density (BMD): A Systematic Review and Meta-Analysis

Background: During lactation, metabolic changes in the bone in different areas of the body may affect the amount of bone mineral density. The aim of this study was to determine the relationship between breastfeeding and bone mineral density in women. Materials and Methods: In this study, articles were searched at Cochran, Medline (via PubMed), Scopus, and Web of Science databases until June 2018. The search procedure was conducted with keywords related to breastfeeding and bone mineral density. The mean (SD) of bone mineral density was extracted in the lumbar spine and femoral neck. Funnel plot and Egger's test was used for publication bias assessing and I-2 index were used for heterogeneity. Results: In this study, 10 articles involving 3,613 healthy women included for Meta analyze. We observed the decreasing trend in mean bone mineral density (BMD) of lumbar spine, femur neck in non-breastfeeding subgroup to 24 months or more breastfeeding subgroup. BMD of lumbar spine in non-breastfeeding women were [M: 0.96, 95% confidence interval [CI]; 0.89-1.02, P= 0.000], in subgroup with more than 24 months breastfeeding the BMD were [M: 0.87, 95% CI; 0.79-0.95, P= 0.000]. The femoral neck BMD in non-breastfeeding were [M: 0.80 95% CI; 0.73-0.87, P= 0.000], and in subgroup with more than 24 months breastfeeding the BMD were [M: 0.76, 95% CI; 0.71-0.81, P= 0.000]. In subgroup analyze, the mean BMD in Asian and postmenopausal sub-group was lower than others. Conclusion: The results of this study showed that breastfeeding have reduced effect on bone mineral density in the lumbar spine and femoral neck of women, but there were high heterogeneity in subgroup analyze, so we recommended another studies in homogenous group of women.