Association between breastfeeding and breast, thyroid, and cervical cancer among Korean adult women based on the Korean Genome and Epidemiology Study: a cohort study

PURPOSE: The purpose of this study was to explore the association between breastfeeding and the prevalence of breast, thyroid, and cervical cancer among Korean adult women. METHODS: The study was a secondary analysis of data from the Korea Genome and Epidemiology Study. The final samples were 113,944 Korean women among 173,205 urban-based cohort participants collected between 2004 and 2013 for adults aged forty and over. To determine the association between female cancers and breastfeeding experience, the number of childbirth, and total breastfeeding duration, logistic regression analysis was done. The demographic characteristics, health behavior, and female history were adjusted. RESULTS: The prevalence of breast cancer was 1.37 times higher in the non-breastfeeding group than in the breastfeeding group. Compared to having breastfed for more than 36 months, the prevalence of thyroid cancer was 1.68 times higher at breastfeeding for 13 to 36 months, 1.67 times higher at breastfeeding for 6 to 12 months, and 2.06 times higher at breastfeeding less than 6 months. Also, the prevalence of cervical cancer was 1.54 times higher at breastfeeding for 13 to 36 months, compared to breastfeeding for more than 36 months. CONCLUSION: This study found that breastfeeding experience and a longer breastfeeding duration are associated with reduced risk of breast, thyroid, and cervical cancer in Korean women. It can be used as a basis for encouraging breastfeeding, and suggests further research on modifiable factors that reduce cancer risks.