Breastfeeding and the maternal risk of type 2 diabetes: a systematic review and dose-response meta-analysis of cohort studies.
OBJECTIVE
Breastfeeding has been associated with reduced risk of maternal type 2 diabetes in some cohort studies, but the evidence from published studies have differed with regard to the strength of the association. To clarify this association we conducted a systematic review and dose-response meta-analysis of breastfeeding and maternal risk of type 2 diabetes.


RESULTS
We conducted a systematic review and dose-response meta-analysis of prospective studies of breastfeeding and maternal risk of type 2 diabetes. We searched the PubMed, Embase and Ovid databases up to September 19th 2013. Summary relative risks were estimated using a random effects model. Six cohort studies including 10,842 cases among 273,961 participants were included in the meta-analysis. The summary RR for the highest duration of breastfeeding vs. the lowest was 0.68 (95% CI: 0.57-0.82, I(2) = 75%, p heterogeneity = 0.001, n = 6). The summary RR for a three month increase in the duration of breastfeeding per child was 0.89 (95% CI: 0.77-1.04, I(2) = 93%, p heterogeneity < 0.0001, n = 3) and the summary RR for a one year increase in the total duration of breastfeeding was 0.91 (95% CI: 0.86-0.96, I(2) = 81%, p heterogeneity = 0.001, n = 4). There was little difference in the summary estimates whether or not BMI had been adjusted for. The inverse associations appeared to be nonlinear, p nonlinearity < 0.0001 for both analyses, and in both analyses the reduction in risk was steeper when increasing breastfeeding from low levels.


CONCLUSIONS
This meta-analysis suggests that there is a statistically significant inverse association between breastfeeding and maternal risk of type 2 diabetes.
Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway; Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, United Kingdom. Electronic address: d.aune@imperial.ac.uk.
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D
Aune
Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, United Kingdom.
T
T
Norat
Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
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P
Romundstad
Department of Public Health and General Practice, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
L J
LJ
Vatten
D001942:Breast Feeding; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D005260:Female; D006801:Humans; D011247:Pregnancy; D012307:Risk Factors
Breastfeeding; Cohort studies; Lactation; Meta-analysis; Type 2 diabetes