Lactation duration and ischemic heart disease among parous postmenopausal females from a prospective cohort study.

Background: This study aimed to evaluate the association of lactation duration with incident ischemic heart disease (IHD) and to determine the potential health gains from scaling up breastfeeding practice.

Methods: 130,147 parous postmenopausal females without IHD were included at baseline (2004-2008) from the China Kadoorie Biobank study. Lactation duration was self-reported and measured as lifetime, per child, and first child, respectively. Incident IHD was identified during follow-up (2004-2015). The dose-response associations between lactation duration and IHD were examined using Cox models with restricted cubic splines. Stratification analyses were conducted by socioeconomic status (SES) and residence. The number of preventable IHD cases was estimated using the population attributable fraction and potential impact fraction in various scenarios.

Results: The study shows that parous postmenopausal females who ever lactated have significantly lower risks of IHD, with adjusted hazard ratios (aHRs) varying from 0.71 (95%CI: 0.63-0.80) to 0.85 (95%CI: 0.75-0.96) for a lifetime, from 0.70 (0.63-0.78) to 0.82 (0.72-0.93) for per-child, and from 0.80 (0.74-0.87) to 0.92 (0.85-0.99) for the first-child, appearing as U-shaped associations. Similar associations are found in females with low SES and urban residence. The scaling up of breastfeeding to near-universal levels could have prevented up to 115,000 new IHD cases among Chinese females aged over 40 years in 2019.

Conclusions: Lactation demonstrates potential benefits in reducing IHD risk, appearing as U-shaped associations among Chinese parous postmenopausal females, especially for those with low SES in urban areas. Scaling up breastfeeding practices serves as a promising strategy for reducing the IHD burden in China.