Lactation Duration and Progression to Diabetes in Women Across the Childbearing Years

Abstract

IMPORTANCE Lactation duration has shown weak protective associations with incident diabetes (3%-15% lower incidence per year of lactation) in older women based solely on self-report of diabetes, studies initiated beyond the reproductive period are vulnerable to unmeasured confounding or reverse causation from antecedent biochemical risk status, perinatal outcomes, and behaviors across the childbearing years.OBJECTIVE To evaluate the association between lactation and progression to diabetes using biochemical testing both before and after pregnancy and accounting for prepregnancy cardiometabolic measures, gestational diabetes (GD), and lifestyle behaviors.DESIGN, SETTING, AND PARTICIPANTS For this US multicenter, community-based 30-year prospective cohort study, there were 1238 women from the Coronary Artery Risk Development in Young Adults (CARDIA) study of young black and white women ages 18 to 30 years without diabetes at baseline (1985)(1986) who had 1 or more live births after baseline, reported lactation duration, and were screened for diabetes up to 7 times during 30 years after baseline .EXPOSURES Time-dependent lactation duration categories (none, >0 to 6 months, >6 to <12 months, and Ն12 months) across all births since baseline through 30 years.MAIN OUTCOMES AND MEASURES Diabetes incidence rates per 1000 person-years and adjusted relative hazards (RH) with corresponding 95% CIs, as well as proportional hazards regression models adjusted for biochemical, sociodemographic, and reproductive risk factors, as well as family history of diabetes, lifestyle, and weight change during follow-up. RESULTSOverall 1238 women were included in this analysis (mean [SD] age, 24.2 [3.7] years; 615 black women). There were 182 incident diabetes cases during 27 598 person-years for an overall incidence rate of 6.6 cases per 1000 person-years (95% CI, 5.6-7.6); and rates for women with GD and without GD were 18.0 (95% CI, 13.3-22.8) and 5.1 (95% CI, 4.2-6.0), respectively (P for difference < .001). Lactation duration showed a strong, graded inverse association with diabetes incidence: adjusted RH for more than 0 to 6 months, 0.75 (95% CI, 0.51-1.09); more than 6 months to less than 12 months, 0.52 (95% CI, 0.31-0.87), and 12 months or more 0.53 (0.29-0.98) vs none (0 days) (P for trend = .01). There was no evidence of effect modification by race, GD, or parity. CONCLUSIONS AND RELEVANCEThis study provides longitudinal biochemical evidence that lactation duration is independently associated with lower incidence of diabetes. Further investigation is required to elucidate mechanisms that may explain this relationship.

Breastfeeding and long‐term maternal metabolic health in the HUNT Study: a longitudinal population‐based cohort study

“…reverse causality), which predisposes to both short BF duration and metabolic disease. If so, this could explain both the positive association between BF and later good metabolic health found in previous observational studies, and also the lack of such an effect in the PROBIT study . By exploring development in metabolic health parameters in different BF‐duration groups, we aimed to disentangle effects of BF on long‐term maternal metabolic health from effects of pre‐pregnant health on BF duration and long‐term metabolic health.…”

“…Previous large observational studies report positive effects of BF on maternal metabolic health, such as reduced risk of diabetes, hypertension, hyperlipidaemia, and cardiovascular disease later in life . Some studies have found that women who breastfeed lose weight faster postpartum and that BF duration is inversely correlated with body mass index (BMI) and waist circumference (WCF) .…”

The obstetrician's role in preventing cardiometabolic disease

“…Firstly, they should promote breastfeeding. There is strong evidence from a 30‐year prospective cohort study that lactation duration is associated with a lower incidence of diabetes in women with and without GDM …”

“…There is strong evidence from a 30-year prospective cohort study that lactation duration is associated with a lower incidence of diabetes in women with and without GDM. 42 Secondly, obstetricians should communicate to women and their primary care providers that the rate of progression to T2DM is highest within 3-6 years of GDM. 8,9 The NICE 2015 guideline for diabetes in pregnancy recommends that women with GDM are all offered diet and lifestyle advice and a fasting blood glucose check between 6 and 13 weeks postpartum, followed by annual HbA1c screening thereafter.…”

Lactation intensity and duration to postpartum diabetes and prediabetes risk in women with gestational diabetes

“…3,4 Several studies have found a graded association between lactation duration and the risk of diabetes. [5][6][7][8][9][10][11] However, selfreported diagnoses of diabetes were used in some of these studies rather than the lab measurement to define the major outcome. 5,9 Moreover, few studies have assessed the association of lactation intensity and duration with postpartum diabetes risk among women with GDM, and their results remain inconsistent because of the relatively small sample sizes of women with GDM, few cases of type 2 diabetes, 10,11 and short follow-up time.…”