As a researcher working on ovarian cancer I have spent much time considering how reproductive factors influenced the risk of developing ovarian cancer. Reproductive events are an integral part of a woman’s life, beginning from the age when they begin to menstruate, considerations of contraception and child bearing, through to the menopause.
It was apparent that compared with the large number of research studies that had examined reproductive factors in relation to risk of developing women’s cancers (such as breast, endometrial and ovarian cancer); fewer studies have investigated how reproductive events influenced women’s long-term health.
What did we do?
The focus of our study, published today in BMC Medicine, was to evaluate a range of reproductive factors such as having children, breastfeeding, oral contraceptive use, and age at menarche, in relation to risk of all-cause mortality and cause-specific mortality.
This study used data from a large prospective cohort study, the European Investigation into Cancer and Nutrition, that included >500,000 men and women mostly from the general population who resided in ten European countries (1992-2000).
We hoped to provide insights to understand the influence that reproductive characteristics may have on women’s long-term health.
Our study evaluated the reproductive histories of 322,972 women. When participants enrolled in the study they completed questionnaires about their reproductive characteristics, other lifestyle factors and diet and they have been followed since their time of enrolment to identify participants who develop certain diseases including cancer and/or those who died. In this study we hoped to provide insights to understand the influence that reproductive characteristics may have on women’s long-term health.
What did we find?
Interesting findings from our study were that the risk of all-cause mortality was lower for women who had children versus never had children, those who had ever versus never breastfed, women that had used versus never used oral contraceptives (non-smokers only), and those who experienced their first menstrual period (menarche) at an older age.
What is interesting to consider is how these reproductive factors may relate to mortality risk. For example, we and others, such as articles published here and here) observed that a later age at menarche was associated with a lower risk of all-cause, total cancer and circulatory disease mortality.
Hypothesized mechanisms that could explain the possible link between the age at menarche for example and risk of mortality outcomes later in life are that having an early age at menarche may be associated with: higher blood pressure and glucose intolerance; or increased body fat in early adulthood; or obesity in adulthood.
The future of our findings
Results from our study could be used to assist in the development of strategies to improve the long-term health of women. One of the biggest challenges is that reproductive factors themselves are not modifiable (as compared with other lifestyle factors that you could possibly change like diet and exercise levels).
However, it may be possible to mimic the effects of a reproductive exposure if the relevant biological mechanisms can be identified.
For example, it is known that breastfeeding protects against breast cancer development, therefore if studies can identify the underlying mechanisms for this association then it may be possible to develop a drug that mimics the effects of breastfeeding on the breast.
Along these lines, an important area to expand on this research is to clarify the mechanisms that link these reproductive exposures to mortality risk.