Background: Numerous studies have reported associations between the type of feeding during infancy and subsequent cardiovascular risk factors. Only 2 studies have evaluated the relation between having been breastfed and the risk of adult cardiovascular events.
Methods: We examined this association among 87,252 female participants of the longitudinal Nurses' Health Study. Participants (all born between 1921 and 1946) reported in 1992 whether and for how long they were breastfed. During 8 years of follow up, there were 1099 cases of coronary heart disease and 940 strokes among women who knew whether they had been breastfed. We used proportional hazards models to estimate hazard ratios for cardiovascular events, adjusting for changing adult risk factors.
Results: Compared with women who were never breastfed, women who were breastfed had hazard ratios of 0.92 (95% confidence interval = 0.80-1.05) for coronary heart disease and 0.91 (0.79-1.06) for stroke, after adjustment for age, birthweight, and smoking. When body mass index was also included in the model, the results were similar. Looking within subgroups of stroke, hazard ratios were 0.86 (0.70-1.07) for ischemic stroke and 1.01 (0.70-1.46) for hemorrhagic stroke. Comparing women who were breastfed at least 9 months with those who were not breastfed, the hazard ratios were 0.84 (0.69-1.03) for coronary heart disease and 1.00 (0.81-1.23) for stroke. Breastfeeding history was not associated with high blood pressure in adulthood.
Conclusions: These data suggest, but cannot establish, that breastfeeding in infancy may be associated with a small reduction in risk of ischemic cardiovascular disease in adulthood.