Sustained Reduction of Subclinical Inflammation in the years after Breastfeeding.

Context: Lactation is associated with lower future risk of cardiovascular disease in women but the mechanism(s) underlying this relationship remain unclear.

Objective: We sought to characterize the relationship between duration of exclusive breastfeeding and cardiovascular risk factors over the first 5-years postpartum.

Design/setting/patients: In this prospective cohort study, 328 women underwent serial cardiometabolic characterization (anthropometry, blood pressure, lipids, fasting glucose, adiponectin, C-reactive protein (CRP)) at 1-year, 3-years, and 5-years postpartum.

Outcome: Cardiovascular risk factors in 3 groups defined by duration of exclusive breastfeeding, as follows: <3 months (n=107), 3-6 months (n=101), and ≥6 months (n=120).

Results: The prevalence of metabolic syndrome did not differ between the groups at 3-years but, by 5-years postpartum, was higher in women who had exclusively breastfed <3 months than in those who did so for 3-6 and ≥6 months, respectively (14.0% vs 6.9% vs 4.2%; p=0.02). However, after adjustment for covariates (including BMI), there were no significant differences between groups in blood pressure, glucose, LDL cholesterol, HDL cholesterol, triglycerides or adiponectin. Indeed, the only cardiovascular risk factor difference that persisted after covariate adjustment was that women who had exclusively breastfed <3 months had higher CRP at both 3-years (p=0.04) and 5-years (p=0.01). Moreover, generalized estimating equation analyses with adjustment for covariates (including time-dependent BMI) showed that CRP remained higher over time in these women, as compared to their peers, from 1-year to 3-years to 5-years postpartum (p=0.03).

Conclusion: Sustained reduction of subclinical inflammation may contribute to the cardioprotective effect of lactation in women.