Duration of Lactation and Incidence of Type 2 Diabetes

Abstract

Context Lactation is associated with improved glucose and insulin homeostasis, independent of weight change.Objective To evaluate the association between lactation history and incidence of type 2 diabetes. Design, Setting, and Participants Prospective observational cohort study of 83 585 parous women in the Nurses' Health Study (NHS) and retrospective observational cohort study of 73 418 parous women in the Nurses' Health Study II (NHS II). Main Outcome Measure Incident cases of type 2 diabetes mellitus. Results In the NHS, 5145 cases of type 2 diabetes were diagnosed during 1 239 709 person-years of follow-up between 1986 and 2002, and in the NHS II, 1132 cases were diagnosed during 778 876 person-years of follow-up between 1989 and 2001.Among parous women, increasing duration of lactation was associated with a reduced risk of type 2 diabetes. For each additional year of lactation, women with a birth in the prior 15 years had a decrease in the risk of diabetes of 15% (95% confidence interval, 1%-27%) among NHS participants and of 14% (95% confidence interval, 7%-21%) among NHS II participants, controlling for current body mass index and other relevant risk factors for type 2 diabetes.Conclusions Longer duration of breastfeeding was associated with reduced incidence of type 2 diabetes in 2 large US cohorts of women. Lactation may reduce risk of type 2 diabetes in young and middle-aged women by improving glucose homeostasis.

Associations Between Parity, Breastfeeding, and Risk of Maternal Type 2 Diabetes Among Postmenopausal Women

“…When we combined parity history and breastfeeding history, we observed that women with five or more term pregnancies had increased diabetes risk, regardless of breastfeeding duration, but that women with one to four term pregnancies did not have higher diabetes risk when they breastfed more than 12 months in total or each child more than 3 months. Our findings are consistent with previous studies ( 9 , 22 ). For example, a prospective study among 52,731women observed that compared with nulliparous women, parous women who did not breastfeed had greater risk of diabetes (odds ratio 1.48, 95% CI 1.26–1.73, P < 0.001), whereas among parous women who breastfed, the risk for diabetes was not significantly increased ( 9 ).…”

Lactation and cardiovascular risk factors in mothers in a population-based study: the HUNT-study

“…Our findings are consistent with recent studies showing that the favourable effects of lactation on maternal metabolic health persist post weaning [7,8,11,17-20] and thereby further supporting the notion that lactation may induce long-term beneficial effects on maternal blood pressure, weight [21], diabetes [6,18], components of the metabolic syndrome [5,19] and cardiovascular health [7,11,17]. Previous studies have shown that the beneficial effect of lactation on cardiovascular risk factors seems to wane with time since last birth [6,11,18].…”

Parity, Breastfeeding, and the Subsequent Risk of Maternal Type 2 Diabetes

“…Other large prospective studies suggest risk reductions in diabetes of ∼15–20% per year of lactation (1–3); our findings concur with this estimate. There is less consistency among studies examining the association between parity and diabetes, with some suggesting either no effect (8) or a small (9) to moderate (10,11) increase in risk.…”

“…Our results confirm previous work suggesting that parous women who breastfeed can reduce their risk of developing type 2 diabetes in later life and that the benefit increases the longer the duration of breastfeeding (1–3). What is novel is, compared with nulliparous women, women who have children but do not breastfeed have an increased risk of diabetes in later life; however, this excess risk may be avoided in women who breastfeed.…”