September 10, 2010 — Breast-feeding for less than 1 month is linked to an increased risk for type 2 diabetes, according to the results of a study reported in the September issue of the American Journal of Medicine.
"We have seen dramatic increases in the prevalence of type 2 diabetes over the last century," said lead author Eleanor Bimla Schwarz, MD, MS, from the University of Pittsburgh in Pittsburgh, Pennsylvania, in a news release. "Diet and exercise are widely known to impact the risk of type 2 diabetes, but few people realize that breastfeeding also reduces mothers' risk of developing the disease later in life by decreasing maternal belly fat."
The goal of the study was to examine the associations between duration, exclusivity, and consistency of lactation with the risk for type 2 diabetes in a well-studied cohort of women, aged 40 to 78 years, representative of the overall population. This cohort consisted of 2233 female members of Kaiser, a large, integrated healthcare delivery organization in California, who were enrolled in the Reproductive Risk factors for Incontinence Study at Kaiser (RRISK), between 2003 and 2008. The investigators controlled for age, parity, race, education, hysterectomy, physical activity, tobacco and alcohol use, family history of diabetes, and body mass index using multivariable logistic regression.
Of the study sample, 1828 were mothers; more than half (56%) had breast-fed an infant for at least 1 month. Compared with nulliparous women, those who consistently breast-fed all of their children for at least 1 month had a similar adjusted risk for type 2 diabetes (odds ratio [OR], 1.01; 95% confidence interval [CI], 0.56 - 1.81), whereas mothers who had never breast-fed an infant had greater risk (OR, 1.92; 95% CI, 1.14 - 3.27). Compared with mothers who exclusively breast-fed for 1 to 3 months, those who never exclusively breast-fed were more likely to have gone on to have type 2 diabetes (OR, 1.52; 95% CI, 1.11 - 2.10).
"Risk of type 2 diabetes increases when term pregnancy is followed by <1 month of lactation, independent of physical activity and body mass index in later life," the study authors write. "Mothers should be encouraged to exclusively breast-feed all of their infants for at least 1 month."
Limitations of this study include observational design subject to residual confounding, recall or reporting bias leading to possible misclassification of women's lactation history, and lack of data on women's level of obesity or insulin resistance at the time of pregnancy.
"Our study provides another good reason to encourage women to breastfeed their infants, at least for the infant's first month of life," said Dr. Schwarz. "Clinicians need to consider women's pregnancy and lactation history when advising women about their risk for developing type 2 diabetes."
The National Institutes of Health's National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Child Health and Development supported this study. The study authors have disclosed no relevant financial relationships.
Am J Med. 2010;123:863.e1-863.e6.
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