Leaders in Pharmaceutical Business Intelligence (LPBI) Group

Reporter and Curator: Dr. Sudipta Saha, Ph.D.

Early menopause, defined as the cessation of ovarian function before the age of 45 years, affects approximately 10% of women in Western populations. Current research suggests that women who experience early menopause are at increased risk of premature mortality, cognitive decline, osteoporosis, and cardiovascular disease.

The reproductive aging process is characterized by the gradual decrease in both quantity and quality of oocytes within ovarian follicles. The number of oocytes a woman is born with, the rate of loss of those oocytes during the life span because of the process of atresia, and the threshold number of oocytes needed to produce sufficient hormones to maintain menstrual cyclicity have been identified as determinants of age at menopause.

Women who breastfed their infants exclusively for seven to 12 months may have a significantly lower risk of early menopause than their peers who breastfed their infants for less than a month, according to an analysis funded by the National Institutes of Health. The study was conducted at University of Massachusetts provide the strongest evidence to date that exclusive breastfeeding may reduce the risk of early menopause. The study also suggests that pregnancy can reduce the risk of early menopause.

Previous studies have suggested that menopause before age 45 (early menopause) increases the risk of early death, cognitive decline, osteoporosis and cardiovascular disease. Smaller studies have found evidence linking pregnancy and breastfeeding with later menopause, but because of their size and other limitations, the results are inconclusive. Moreover, the earlier studies focused on timing of menopause and not on the risk of early menopause.

In the present study, researchers analyzed data from more than 100,000 women ages 25 to 42 years. Every two years, from 1989 to 2015, the participants responded to detailed questionnaires, providing health information and medical history, including pregnancy history. Compared to women who had never been pregnant or who had been pregnant for less than six months, women who had one full-term pregnancy had an 8% lower risk of early menopause. Those who had two pregnancies had a 16% lower risk, and those who had three pregnancies had a 22% lower risk.

Women who breastfed had an even smaller risk for early menopause. Those who breastfed for a total of 25 months or more during their premenopausal years had a 26% lower risk than women who breastfed for less than a month. Similarly, women who breastfed exclusively seven to 12 months had a 28% lower risk of early menopause, compared to those who breastfed for less than a month.

It is yet to be determined why pregnancy and breastfeeding lower the risk of early menopause. However, researchers theorize that because pregnancy and breastfeeding halt ovulation, the slowing of the egg loss may delay menopause. This study population is fairly homogeneous with respect to race and ethnicity, but it is expected that the physiological association between the reproductive factors of parity, breastfeeding, and early menopause would not differ substantially by race/ethnicity. Additional evaluation of these associations in more diverse populations as well as further study of the association with anti-Müllerian hormone levels are important.

References:

https://www.nih.gov/news-events/news-releases/pregnancy-breastfeeding-may-lower-risk-early-menopause-nih-study-suggests

https://www.ncbi.nlm.nih.gov/pubmed/31968114

https://www.ncbi.nlm.nih.gov/pubmed/19733988

https://www.ncbi.nlm.nih.gov/pubmed/18192670

https://www.ncbi.nlm.nih.gov/pubmed/7856687

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2615483/