Risks of Breast Cancer: How are Periods Involved?

October is Breast Cancer Awareness Month, and in this edition of our newsletter, we are highlighting the strong connections between menstruation and breast cancer risk. Breast cancer remains one of the most common cancers among women (The University of Kansas Cancer Center), and the hormones estrogen and progesterone play a significant role in its development. Anyone who menstruates may be affected by these hormonal factors. In general, the longer a person menstruates over their lifetime, the greater their overall exposure to these hormones and consequently, the higher their risk of developing breast cancer. While the increases in risk are relatively small, this information is not widely known and is thus important to share.

First Periods

The age a person begins menstruating can influence their breast cancer risk. Having a younger than average first period, specifically age 11 and younger, increases the risk of developing breast cancer later in life. This is because the body produces more estrogen and progesterone for longer, exposing the breast tissue to more of the hormones. Estrogen, in particular, has been strongly linked to breast cancer cell production (Canadian Cancer Society). 

Menopause

Experiencing a later menopause, specifically later than 55, similarly increases the risk of developing breast cancer. Much like with early periods, late menopause extends the reproductive lifespan and allows the breast cells to be exposed to estrogen and progesterone for a longer time, raising the likelihood of breast cancer. In contrast, going through early menopause, specifically younger than 45, decreases a person's risk of developing breast cancer (Canadian Cancer Society). 

Childbearing

The number of children a person bears, and how late in their life they have their first child (if at all) alters the risk of developing breast cancer. In this case, it is much less straightforward than with early periods and late menopause. It has been found that the risk of developing breast cancer decreases with each full term pregnancy (Eaton). Additionally, becoming pregnant at an earlier age, younger than twenty, has also been seen to decrease the risk. 

Understanding how reproductive factors influence breast cancer risk can empower individuals to have more informed conversations with their healthcare providers. While these hormonal influences are not within our control, awareness can lead to earlier screenings and proactive health decisions. The interplay between menstruation, menopause, and childbearing highlights the complexity of health, especially in women. This Breast Cancer Awareness Month, we encourage everyone to learn more and share this knowledge with others.

Works Cited

Canadian Cancer Society / Société canadienne du cancer. “Risks for Breast Cancer.” Canadian Cancer Society, Dec. 2024, cancer.ca/en/cancer-information/cancer-types/breast/risks#:~:text=Progesterone%20is%20made%20mainly%20by,growth%20of%20some%20breast%20cancers. 

Eaton, Lynn. “Early Periods and Late Childbearing Increase Risk of Breast Cancer, Study Confirms.” BMJ : British Medical Journal, BMJ Publishing Group Ltd, 16 Feb. 2002, pmc.ncbi.nlm.nih.gov/articles/PMC1172033/. 

“Most Common Cancers in Women & How to Detect Them Early.” The University of Kansas Cancer Center, The University of Kansas Cancer Center, 21 Aug. 2020, www.kucancercenter.org/news-room/blog/2020/08/most-common-cancers-women-how-to-detect-them-early.