Health problems experienced early in life are linked to childlessness later in life, a new study suggests.
Researchers from Harvard and Oxford University found that behavioral health problems – such as alcoholism and schizophrenia – had the greatest impact on childlessness among men diagnosed in their early twenties.
Women were most likely to be childless due to autoimmune and inflammatory diseases such as multiple sclerosis, cardiovascular disease and type 2 diabetes when they were diagnosed in their early 20s.
The long list of 74 different conditions that increase a man or woman's likelihood of becoming childless later in life adds to the range of factors that have pushed U.S. birth rates into freefall, including financial pressures and the pursuit of professional goals .
Diagnoses of birth defects and other disorders from birth, as well as mental health problems and disorders that affect the nervous system, such as MS and juvenile arthritis, were among the diagnoses with the strongest impact on a person's ability to have a child.
The study, made up of people from Sweden and Finland, examined the reasons for involuntary childlessness, meaning people wanted to start a family but were unable to do so, mainly due to mental disorders and metabolic conditions such as diabetes.
The graph above shows the 74 conditions shown to have the most statistically significant association with childlessness in later life. In many cases, the significances were higher for one gender than for the other
Involuntary childlessness is an umbrella term that covers a wide area. A person may be involuntarily childless because he or she is struggling with infertility, or perhaps an underlying health condition, such as blood clots or heart disease, makes having a child or becoming pregnant unsafe.
Having a conduct disorder can also leave someone involuntarily childless if they know that the underlying mental health problem could be passed on to their child, or if their disorder is so severe that they would not be able to care for a child.
Of the 74 diseases associated with childlessness, which in most cases was involuntary, more than half consisted of behavioral disorders and disabilities such as schizophrenia, cerebral palsy, alcohol and drug addiction and antisocial personality disorder.
Other non-mental conditions that were also associated with increased rates of childlessness included high blood pressure, blood clotting disorders, vaginal infection and lack of regular periods.
Researchers from Harvard University, the University of Helsinki and the Karolinska Institutet in Sweden included 2.5 million subjects from Finland and Sweden.
They looked at data from 1.4 million women (born between 1956 and 1973) and 1.1 million men (born between 1956 and 1968).
Women who were between the ages of 16 and 20 when diagnosed with obesity, considered one of the most critical public health problems facing the U.S., were more likely to be childless than women who were born at a young age were diagnosed.
Overall, the strongest association with childlessness occurred in women when the disease was first diagnosed between ages 21 and 25.
Most research on reasons for childlessness has focused on women, but because the researchers focused on 71,524 full sister and 77,622 full brother pairs who showed differences in their childlessness status, they were able to identify differences between genders.
Diabetes-related diseases and birth defects had stronger associations with women
Schizophrenia and acute alcohol intoxication were more strongly associated with childlessness in men
It was this focus on both women and men that led the researchers to find that while mental problems were most influential among men, metabolic and endocrine problems such as diabetes had a greater impact on women's childlessness.
Dr. Andrea Ganna, Director of the Institute for Molecular Medicine Finland (FIMM), said: 'By assessing the role of multiple diseases in early life on childlessness for 2.5 million people in Finland and Sweden, this study paves the way for a better understanding of how disease contributes to involuntary childlessness and the need for better public health interventions.'
A quarter of the 1.1 million men surveyed were childless, compared with almost 17 percent of the 1.4 million women.
In men, the impact of diseases on childlessness was greatest when the diseases were diagnosed between the ages of 26 and 30.
Dr. Aoxing Liu, lead author of the study and a researcher at the University of Helsinki, said: 'Several factors are driving an increase in childlessness worldwide, with delayed parenthood a major contributor that may increase the risk of involuntary childlessness.'
Their findings were published in the journal Nature Human behavior.
US population growth is slowing as more women choose to forego having children and infertility rates rise worldwide, and not just in the US.
The number of births in America has been declining for years and has fallen 22 percent nationwide since 2007, data shows. The downward trend is prompting warnings that the US is now on an irreversible path of economic decline.
Men now have their first child on average at the age of 26.4, while women give birth for the first time at the age of 23.7. Both have increased dramatically over the past twenty years
The number of American women with at least one child has fallen to just 52.1 percent, while the number of men has fallen to 39.7 percent in 2019
Data from the Centers for Disease Control and Prevention shows that about one in five women – 19 percent – cannot become pregnant after a year of trying. In addition, more than a quarter of women in this group have difficulty becoming pregnant or carrying a pregnancy to term.
The pressure on women to start a family can be overwhelming. More and more women are also choosing to delay childhood and focus on their careers and building their financial stability.
The average age of new mothers in America has now increased from 21 to 26. For fathers, it has increased from 27 to 31.
A 2020 study found that 60 percent of the participants reported that they postpone having children because they don't have enough money, and more than half said they want to earn a higher salary first.
At the same time, three in five millennials were willing to postpone milestones in their lives until they reached a certain job title or level in their career.