Breastfeeding mum with baby in her arm
Breastfeeding lowers mothers’ risk of cardiovascular disease, according to a meta-analysis evaluating data from over one million women. © Paulo Sousa/Noun Project

Women who have breastfed during their lives are less likely to suffer coronary heart disease, a heart attack or a stroke. While this much has been evidenced in a publication by the Medical University of Innsbruck (MUI), the exact manner in which breastfeeding improves cardiological health is unclear. Lena Tschiderer, principal author of the study, puts forward the “reset hypothesis” as a possible explanation. According to this theory, breastfeeding restores the female metabolism to the state before pregnancy. “During pregnancy, fat reserves are built up in the body, which the woman needs during this time. Breastfeeding enables mothers to return to their previous levels more quickly, regarding inter alia the risk factor cholesterol,” says Tschiderer.

Most deaths occur from cardiovascular diseases

Tschiderer, a mathematician at the MUI's Institute of Health Economics, conducts statistical analyses of data sets covering several hundred thousand people. Her intention is to find out how the different phases in a woman’s life affect the cardiovascular system. It is a particularly relevant issue, given that this group of diseases has topped the list of causes of death in Austria for decades and is responsible for one in every three deaths.

Tschiderer's project is funded by the Austrian Science Fund FWF in the context of its Hertha-Firnberg Postdoc Program. In addition to the breastfeeding factor, Tschiderer was also able to discover other influences on women's heart health, such as the occurrence of high blood pressure during pregnancy or the age at the onset of menopause.

Who is affected by heart attack & co.?

It had been assumed for a long time that it is typically men who are affected by cardiovascular disease. If asked to picture a person having a heart attack or stroke one is likely to picture a man with the classic risk factors: obesity, smoking, alcohol, stress. But women are exposed to the same level of risk. “Globally, one third of both women and men die from cardiovascular diseases, but the diseases often develop in a different form,” emphasizes Tschiderer. Her analyses focused on stages of life that are typically “female” from a biological and medical point of view and relate to fertility or pregnancy.

Young woman with long blonde hair in front of two computer screens.
Lena Tschiderer, a mathematician at the Medical University of Innsbruck, conducts statistical analyses of huge data sets, to find out how the different phases in a women's life affect the cardiovascular system. © MUI

Pregnancy as the ultimate stress test

According to Tschiderer, the months in which the female body is preparing for childbirth can be seen as a “stress test” for the body. This is shown, for instance, in her study on pre-eclampsia, a complication of pregnancy that is associated with high blood pressure and other symptoms. Tschiderer's calculations found that pre-eclampsia is associated with a higher risk of cardiovascular disease at a later stage in life.

What is even more important, however, is the awareness of this being a causal relationship. “That is why this pre-natal time is also an opportunity to find out whether a woman will have problems with her cardiovascular system later on. It is important to keep affected women under observation after childbirth and to minimize other risk factors,” is how Tschiderer describes the practical relevance of the results.

Early menopause, more strokes

With menopause, i.e. the last menstrual period and the end of fertility in a woman's life, the situation is different. It is known that the phase of life after menopause onset is associated with an increased risk of cardiovascular disease. Tschiderer was also able to show that it depends on the timing: the earlier menopause begins, the higher the risk of stroke – 9 percent higher for every 5 years. In this case, however, the genetic analyses showed that there was no causal link between menopause and stroke. According to Tschiderer, the key to such analyses is to evaluate the data very carefully.

Statistics: handle with care

“I always quote the example that there is a statistical correlation between the frequency of eating ice cream and getting sunburn. But we all know that on sunny days people will quite naturally eat ice cream more often,” says Tschiderer, to elucidate the challenges of such observational studies. For this reason, a central component of her Hertha Firnberg Fellowship was a research stay at the University Medical Center Utrecht in the Netherlands, where she focused specifically on analytical methods relating to the topic of causality.

Together with her Dutch collaboration partners, she found that while early menopause is an indicator of an increased risk of stroke, it is not directly responsible for it. “This means that there could be some third factor that comes into play here – like the sun in the example with the ice cream and sunburn,” says Tschiderer.

More awareness for women's health

Gender-specific differences are currently receiving increasing attention in medicine. “Gender medicine” is the term used to describe healthcare that takes into account both biological and socio-cultural influences on health and the diagnosis and treatment of diseases. One of Tschiderer’s central research concerns is raising awareness of the specific situation of women.

At the same time, her studies illustrate how important it is to evaluate large amounts of data with a critical eye. “There are now numerous studies and data that can be used for such analyses. They can be used to answer many questions, provided you have the statistical tools to work with them. This is true not only of gender medicine, but basically of all areas of medicine,” Tschiderer concludes.

Personal details

Lena Tschiderer studied technical mathematics and neuroscience. At present she is an assistant professor at the Institute of Health Economics at the Medical University of Innsbruck, where she is investigating the specific female influences on cardiovascular health.

The project “Gender differences in atherosclerosis and its consequences” received EUR 243,120 in funding from the Austrian Science Fund FWF and it is set to run until 2026. Thanks to her inclusion in the Hertha Firnberg Postdoc Program for the promotion of early-career women researchers, Tschiderer was able to complete a research stay at the University Medical Center Utrecht in the Netherlands. For her work on breastfeeding she was awarded the 2022 MUI Gender Medicine Research Prize.

Publications

Tschiderer L., Peters S.A.E., van der Schouw Y.T. et al.: Age at Menopause and the Risk of Stroke: Observational and Mendelian Randomization Analysis in 204 244 Postmenopausal Women, in: Journal of the American Heart Association 2023

Tschiderer L., van der Schouw Y.T., Burgess S. et al.: Hypertensive disorders of pregnancy and cardiovascular disease risk: a Mendelian randomisation study, in: Heart 2023

Tschiderer L., Seekircher L., Willeit P., Peters S.A.E.: Assessment of Cardiovascular Risk in Women: Progress so Far and Progress to Come, in: International Journal of Women’s Health 2023

Tschiderer L., Seekircher L., Kunutsor S.K. et al.: Breastfeeding Is Associated With a Reduced Maternal Cardiovascular Risk: Systematic Review and Meta-Analysis Involving Data From 8 Studies and 1 192 700 Parous Women, in: Journal of the American Heart Association 2022

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