A new study by researchers at the University of Helsinki in Finland suggests that both having no children and having significantly more children than average may be associated with a shorter lifespan and faster biological aging. However, scientists stress that these findings represent population-level trends and should not be interpreted as personal health advice.
The study, published in Nature Communications, explores how reproductive patterns may relate to long-term health outcomes.
Study: Evolutionary Theory Offers Possible Explanation
The research draws on the “disposable soma theory,” an idea in evolutionary biology proposing that organisms have limited resources—such as time and energy—which must be divided between reproduction and maintaining the body.
According to the theory, investing heavily in reproduction may leave fewer resources available for bodily repair and maintenance, potentially affecting longevity.
Biologist Mikaela Hukkanen from the University of Helsinki explains that when a large share of energy goes toward reproduction, less may remain for mechanisms that protect and repair the body.
Study Analysed Data From Thousands of Twins
To examine the relationship between childbirth history and mortality, researchers analysed data from 14,836 women who were all twins. Studying twins helped reduce the influence of genetic differences on the findings.
Among these participants, 1,054 women were also tested for biological aging markers. Researchers grouped participants into seven categories based on how many children they had and the timing of those births.
Highest Risks Seen in Two Groups
The analysis revealed that women who had never given birth and those with the highest number of children—an average of nearly seven—showed higher mortality risk and signs of faster biological aging.
Women who had children at a younger age initially appeared to show faster biological aging as well. However, once researchers accounted for lifestyle factors such as alcohol consumption and body mass index (BMI), this link became much weaker.
The associations involving child-free women and those with many children remained even after adjusting for these factors.
Moderate Family Size Linked With Lower Risk
The lowest mortality risk and the slowest biological aging were observed among women who had an average number of children—about two to three—and who had their pregnancies between ages 24 and 38.
Researchers suggest that these patterns may reflect a balance between reproductive investment and the body’s ability to maintain itself over time.
Why Child-Free Women Showed Higher Risk Remains Unclear
While evolutionary theory may help explain the effects of higher reproductive investment, it does not clearly account for the outcomes observed among women without children.
Scientists believe other unmeasured factors—such as existing health conditions—may influence both fertility decisions and long-term health.
Study Shows Long-Term Impact of Life Choices
Epigeneticist Miina Ollikainen notes that biological age can differ from chronological age, and those who are biologically older than their actual age tend to face higher mortality risks.
The findings suggest that life history choices, including reproductive timing, may leave measurable biological effects long before old age.
Findings Show Correlation, Not Cause
Researchers caution that the study identifies statistical associations rather than direct cause-and-effect relationships. Many other influences—including lifestyle, genetics, and socioeconomic conditions—play major roles in determining lifespan and biological aging.
They also emphasize that existing research highlights several psychological and social benefits associated with parenthood.
No Need to Change Personal Decisions
The researchers stress that individuals should not alter their personal plans about having children based on these findings alone.
As Ollikainen explains, decisions about family size are deeply personal and influenced by many factors beyond biological considerations.
Disclaimer: This article is for informational and educational purposes only. It summarizes scientific research in simplified language and should not be considered medical or professional advice.
