Abstract

Objective(s): To prospectively assess the association between lactation duration and incidence of the metabolic syndrome (MetS) among women of reproductive age.

Research Design and Methods: Participants were 1,399 women (39% black, aged 18–30) in the Coronary Artery Risk Development in Young Adults (CARDIA) Study, an ongoing multi-center, population-based, prospective observational cohort study conducted in the United States. Women were nulliparous and free of the MetS at baseline (1985–86) and before subsequent pregnancies, and re-examined 7, 10, 15 and/or 20 years after baseline. Incident MetS cases were identified according to NCEP ATP III criteria. Complementary log-log models estimated relative hazards of incident MetS among time-dependent lactation duration categories by gestational diabetes mellitus (GDM) adjusted for age, race, study center, baseline covariates (BMI, MetS components, education, smoking, physical activity) and time-dependent parity.

Results: Among 704 parous women (620 non-GDM, 84 GDM), there were 120 incident MetS cases in 9,993 person-years (overall incidence rate 12.0 per 1,000 person-years;10.8 for non-GDM, 22.1 for GDM). Increasing lactation duration was associated with lower crude MetS incidence rates from 0–1 month through >9 months (p<0.001). Fully adjusted relative hazards showed that risk reductions associated with longer lactation were stronger among GDM (RHs range:0.14 to 0.56;p=0.03) than non-GDM groups(RHs range:0.44 to 0.61;p=0.03).

Conclusions: Longer duration of lactation was associated with lower incidence of the metabolic syndrome years post-weaning among women with a history of GDM and without GDM controlling for preconception measurements, BMI, socio-demographic and lifestyle traits. Lactation may have persistent favorable effects on women's cardiometabolic health.