Abstract MP67: Lactation Duration and Subsequent Intima Media Thickness in Women During Midlife Controlling for Pre-pregnancy Cardiometabolic Risk Factors: The CARDIA Study

Abstract

Background: Greater lactation duration has been associated with lower incidence of the metabolic syndrome, and self-reported type 2 diabetes and heart disease in women later in life. Two retrospective studies reported higher carotid artery intima-media thickness among parous women who never or inconsistently breastfed, but no clear association with duration. However, lactation history was recalled many years later and heart disease risk factors were not measured before pregnancy. We hypothesized that lactation duration has a graded inverse association with subclinical atherosclerosis in women during mid-life independent of pre-pregnancy cardiometabolic risk factors. Methods: We examined 846 women (46% Black), aged 18-30 years at enrollment in 1985-1986 (baseline) in the biracial Coronary Artery Risk Development in Young Adults (CARDIA) study. Women included delivered 1 or more live births from 1986-2005, had no history of heart disease or diabetes before pregnancies, and had maximum common carotid intima media thickness (ccIMT, mm) measured in 2005-2006 at ages 38-50 years. Lactation duration was recalled within 1 to 4 years of delivery. We categorized women into four lactation groups according to cumulative duration for all post-baseline births; 0-<1 month (n=262), 1-<6 months (n=210), 6-10 months (n=169) and >10 months (n=205). Multiple linear regression models estimated mean ccIMT (95% CI) among lactation categories adjusted for pre-pregnancy cardiometabolic risk factors [BMI, systolic blood pressure (SBP), HDL-C, HOMA-IR], parity, socio-demographics (age, race, education), and smoking. We also assessed weight gain and change in SBP as mediators of the lactation and ccIMT association. Results: Increasing lactation duration showed a graded inverse association with mean ccIMT; differences between >10 months vs. 0<1 month groups ranged from -0.062 from the unadjusted model (p<0.001) and -0.029 from adjusted models (p=0.046) that included pre-pregnancy risk factors and other covariates. Weight gain and SBP change during the 20-year follow up slightly attenuated (~10%) the ccIMT-association with increased lactation duration. Conclusions: Greater lactation duration is associated with lower mean ccIMT independent of cardiometabolic risk factors measured before pregnancy, parity, socio-demographics and smoking. Lactation may have lasting favorable effects on cardiometabolic risk factors for heart disease.