Longer lactation duration tied to lower risks of maternal CAD, stroke

Extended durations of lactation appear to reduce the risk of maternal coronary artery disease (CAD) diagnosed before age 70 years, according to a study. 

A team of investigators conducted this prospective cohort study and followed 6,857 mothers from the Copenhagen Perinatal Cohort who gave birth during 1959–1961 at a median age of 24 years. They assessed the durations of predominant and any lactation at the infant’s 1-year examination. 

Using the national health registers during 1977–2022, the investigators obtained data on diagnoses of CAD (n=701 at 45–70 years; n=593 at >70 years) and stroke (n=410 at 45–70 years; n=535 at >70 years). Using Cox regressions, the investigators estimated the hazard ratios (HRs) and 95 percent confidence intervals (CIs). 

Durations of predominant and any lactation showed an inverse association with the risk of CAD, but not with stroke, when using lactation as a continuous variable. 

Categorical analyses revealed that mothers who lactated for >4 months had a 41-percent reduced risk of CAD (HR, 0.59, 95 percent CI, 0.46–0.75) and a 34-percent lower risk of stroke (HR, 0.66, 95 percent CI, 0.48–0.92) compared with those who lactated for ≤0.5 months. 

These associations weakened (CAD: HR, 0.78, 95 percent CI, 0.60–1.01; stroke: HR, 0.90, 95 percent CI, 0.64–1.27) following adjustments for demographic, metabolic, and reproductive risk factors during pregnancy. Notably, associations with CAD or stroke diagnosed were not seen after 70 years of age. 

"Adjustment for risk factors attenuate the associations, which suggests these factors may partly confound the benefits of lactation on maternal risks of CAD,” the investigators said.