healthHealth and Medicine

Men Also Need To Think About Their "Biological Clock" When Planning Kids


Tom Hale

Senior Journalist

clockMay 13 2019, 13:05 UTC

“Just as people lose muscle strength, flexibility, and endurance with age, in men, sperm also tend to lose 'fitness' over the life cycle.” KieferPix/Shutterstock

When people talk about having a child slightly later in life, the emphasis is often put on women and their so-called “ticking biological clock”. However, new research has shown that men who delay starting a family can also experience fertility problems and run the risk of harming their kids' health.

The new study, published in the journal Maturitas and led by Rutgers University, reviewed 40 years of research looking at pregnancies involving older men and noted a higher risk of premature birth, stillbirth, low birth weight, newborn seizures, and birth defects, such as congenital heart disease and cleft palate. As these children got older, they also had a higher risk of childhood cancers, mental health problems, cognitive disorders, and autism.


There is no clear definition of exactly when in life “advanced paternal age” begins, although most of the studies analyzed suggest it starts sometime between 35 and 45 years of age.

“While it is widely accepted that physiological changes that occur in women after 35 can affect conception, pregnancy and the health of the child, most men do not realize their advanced age can have a similar impact," study author Gloria Bachmann, director of the Women's Health Institute at Rutgers' Robert Wood Johnson Medical School, said in a statement.

Despite these dangers, the trend of older fathers is on the rise. The study found that the number of kids born to fathers over the age of 45 has risen 10 percent in the US over the past 40 years, most likely due to assisted reproductive technology and wider social changes.


The study didn’t specifically look for the exact cause of the links; it simply focused on the associations between advanced paternal age and wider health problems.

Nevertheless, the researchers do cite several factors that could be driving the apparent outcomes. First of all, there’s the natural decline in testosterone that men experience as they age. Second, the quality of sperm is also a concern. Sperm stem cells split and divide around 23 times each year after puberty. Each time this process happens, there’s a potential for errors as DNA gets copied, resulting in around two new mutations each year. Mutations that occur in the sperm at this point can then be passed onto the offspring they go on to produce. As other studies have shown, fathers contribute more mutations to their children than mothers.

On top of health problems, the study also found that older men struggled with fertility issues even if their partner was younger than 25.


“Just as people lose muscle strength, flexibility, and endurance with age, in men, sperm also tend to lose 'fitness' over the life cycle,” Bachmann added.

The team notes that there is much less scientific research and public awareness about the potential consequences of advanced paternal age and, as ever, further research is needed before any firm conclusions can be drawn. However, the researchers call on healthcare professionals to raise more awareness of the potential risks.

They even suggest that some men might want to consider the use of sperm banks "before their 35th or, at least, their 45th birthday" to ensure their swimmers are still in good shape.

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