Sustained Reduction of Subclinical Inflammation in the Years After Breastfeeding.

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

Objective: We sought to characterize the relationship between duration of exclusive breastfeeding and CV risk factors over the first 5 years post partum.

Methods: In this prospective cohort study, 328 women underwent serial cardiometabolic characterization (anthropometry, blood pressure [BP], lipids, fasting glucose, adiponectin, C-reactive protein [CRP]) at 1 year, 3 years, and 5 years post partum. Outcomes were CV risk factors in 3 groups defined by duration of exclusive breastfeeding: less than 3 months (n = 107), 3 to 6 months (n = 101), and 6 months or more (n = 120).

Results: The prevalence of metabolic syndrome did not differ between the groups at 3 years but, by 5 years post partum, was higher in women who had exclusively breastfed for less than 3 months than in those who did so for 3 to 6 and 6 months or more, respectively (14.0% vs 6.9% vs 4.2%; P = .02). However, after adjustment for covariates (including body mass index [BMI]), there were no statistically significant differences between groups in BP, glucose, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, or adiponectin. Indeed, the only CV risk factor difference that persisted after covariate adjustment was that women who had exclusively breastfed for less than 3 months had higher CRP both at 3 years (P = .04) and 5 years (P = .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 post partum (P = .03).

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