Maternal, Perinatal and Pediatric Nutrition
Objectives: Lactation improves short-term glucose metabolism in women, but evidence is scarce about its long-term impact on the development of type 2 diabetes (T2D), especially in high-risk women. We aim to study the association between lactation and long-term risk for T2D among women with a history of gestational diabetes (GDM). We hypothesized that longer duration of total and exclusive lactation would be beneficial for T2D prevention in these high-risk women.
Methods: We followed 4405 women with a history of GDM participating in the Nurses’ Health Study II, a prospective cohort study, from 1991 to 2013. Incident T2D was ascertained through biennial questionnaires and validated supplementary questionnaires. Lactation history was asked in three follow-up questionnaires to calculate lifetime duration of total and exclusive lactation.
Results: We documented 804 incident cases of T2D over 22 years of follow-up among women with a history of GDM. Longer duration of lactation was associated with a lower risk of T2D for both total (Relative Risk [RR] 0.71 [95% Confidence Interval (CI) 0.55-0.92] for >24 months vs. none) and exclusive feeding (RR 0.69 [95% CI 0.53-0.90] for >12 months vs. none) after adjustment for age, race, family history of diabetes, parity, age at first birth, hormone therapy use, smoking status, alcohol intake, physical activity, and dietary intake quality. When further adjusted for baseline body mass index (BMI) and updated changes in adulthood BMI across aging, these associations become attenuated, and only longer duration of exclusive lactation remained significantly associated with a lower T2D risk (p for trend=0.02, across five increasing lactation duration categories).
Conclusions: Longer duration of lactation is associated with a lower risk for T2D among women with a history of GDM. The long-term beneficial impact of lactation, especially exclusive practices, may persist in T2D prevention across lifespan of aging women.