FACTS Spotlight: National Breastfeeding Month
Breastfeeding Duration and Risk of Breast Cancer: A Research Review
By: Katie Hockensmith
Editor’s Note: We are now halfway through National Breastfeeding Month, and the need for further research on the impact of breastfeeding on both mom and baby remains relevant. This week, we are featuring a research review by Katie Hockensmith, a former FACTS elective student and FACTS Ambassador, that highlights the health benefits of breastfeeding for mothers, as it relates to breast cancer risk. Published in the Journal of Human Lactation, this meta-analysis investigates the relationship between breastfeeding mode and breast cancer.
Introduction
Breast cancer is the leading cause of cancer-related deaths for women in underdeveloped countries and the second-leading cause of cancer-related deaths for women in the United States. [1] Among the medical community, it is widely recognized that breastfeeding reduces the risk of breast cancer. However, the effects of exclusive breastfeeding, which is associated with a longer duration of postpartum amenorrhea and reduced exposure to estrogen, remain understudied. Few medical professionals are aware that mothers who are exclusively breastfeeding and meet other criteria can use the Lactational Amenorrhea Method (LAM) as a reliable method for family planning. Additionally, many medical professionals and even patients are unaware of the myriad benefits of breastfeeding for the mother and infant. Despite recommendations from the World Health Organization (WHO) to exclusively breastfeed infants for the first six months after birth, nearly two out of three infants are not exclusively breastfed during that time period. [2] As awareness surrounding the benefits of breastfeeding continues to grow, medical professionals have a responsibility to educate patients surrounding these benefits and advocate for increased access to breastfeeding resources.
“Despite recommendations from the World Health Organization (WHO) to exclusively breastfeed infants for the first six months after birth, nearly two out of three infants are not exclusively breastfed during that time period.”
Methodology
Researchers Unar-Munguía et al. conducted a systematic review of PubMed and EBSCO host articles published from 2005 to 2015 that contained keywords for breast cancer and breastfeeding. [3] A total of 1,921 articles were identified, and 65 met the inclusion criteria. Data regarding breastfeeding modes, duration, and breast cancer diagnoses were extracted from each article and entered into an Excel database. The information was then analyzed for statistical significance using Stata 13.1 software.
The information compiled from each article was used to determine the summary relative risk (SRR), which compares the risk of developing breast cancer across differing breastfeeding behaviors and demographics. The SRR of developing breast cancer was primarily stratified by the breastfeeding mode and dose-response relationship. Breastfeeding modes were further categorized based upon whether the parous woman exclusively breastfed, partially breastfed, or never breastfed. The dose-response relationship was calculated by comparing the total number of months spent breastfeeding (in any mode) with the breast cancer risk. Risk estimations were also stratified by parity status, menopausal status, type of breast cancer, region of the world, and study design.
Results
The results from the meta-analysis support the protective benefit of exclusive breastfeeding against the development of breast cancer. The SRR for breast cancer in women who exclusively breastfed, in comparison with those who had never breastfed, was 0.72; parous women who exclusively breastfed had a 28% lower risk of developing breast cancer than parous women who never breastfed. The SRR for breast cancer in women with any breastfeeding mode was 0.84. Among women who either exclusively or partially breastfed, the average risk of developing breast cancer was 16% lower than parous and nulliparous women who had never breastfed. Results also indicate that the risk of developing breast cancer – the most common cancer diagnosed in American women [1] – is further reduced if breastfeeding is continued for at least 12 months. The dose-response association for all modes of breastfeeding saw the greatest decline in risk of developing breast cancer during the first six months of breastfeeding and after 12 months of breastfeeding.
“Results also indicate that the risk of developing breast cancer – the most common cancer diagnosed in American women – is further reduced if breastfeeding is continued for at least 12 months.”
Discussion
This landmark meta-analysis is the first review conducted on the effects of exclusive breastfeeding and duration, and the association with reduced breast cancer rates. Unfortunately, the results of this meta-analysis are limited by individual study designs of the articles included, which rarely distinguished between exclusive breastfeeding and partial breastfeeding modes. Given that the reported dose-response estimations were based upon risk of breast cancer for all breastfeeding modes, the study may thus lack precision for the individual risks of exclusive breastfeeding, primarily breastfeeding, and partial breastfeeding. Additionally, the results supporting the benefits of exclusive breastfeeding compared to partial breastfeeding lack statistical significance.
Further research that separately analyzes breastfeeding mode and duration is necessary to clarify the relationship between exclusive breastfeeding, breastfeeding duration and breast cancer risk. If dose-response estimations among women who exclusively breastfed continue to support a benefit of breastfeeding after 12 months, the WHO may consider updating their recommendations.
As healthcare professionals, we have a responsibility to support increased rates of exclusive breastfeeding through education, support, and advocacy. The first step must be improved patient education that ensures each woman understands the benefits of exclusive breastfeeding, including presenting the LAM as a valid option of family planning. Additionally, we have the opportunity to connect women with the necessary breastfeeding training and support to help them establish and maintain a successful breastfeeding practice. Lastly, to encourage exclusive breastfeeding among women who return to work during the first six months postpartum, we should advocate for access to flexible scheduling to accommodate lactation breaks, a private area to express milk, and a space to safely store the milk.
Sources
[1] Breast Cancer Statistics And Resources. Breast Cancer Research Foundation. Updated March 12, 2021. Accessed April 2021. https://www.bcrf.org/breast-cancer-statistics-and-resources
[2] Breastfeeding. World Health Organization. Accessed April 2021. https://www.who.int/health-topics/breastfeeding
[3] Unar-Munguía M, Torres-Mejía G, Colchero MA, González de Cosío T. Breastfeeding Mode and Risk of Breast Cancer: A Dose-Response Meta-Analysis. J Hum Lact. 2017;33(2):422-434. doi:10.1177/0890334416683676
ABOUT THE AUTHOR
Katie Hockensmith
Katie Hockensmith is a fourth-year medical student at Chicago College of Osteopathic Medicine at Midwestern University. She was raised in Southwest Missouri where she graduated Summa Cum Laude from Drury University with a double major in Biology and Chemistry. Katie’s desire to provide an improved quality of life for women inspired her to enroll in the FACTS electives. In her position as a FACTS Ambassador, she continues to raise awareness for the FACTS conferences and electives on her campus.
