It’s not just women who have to worry about their ticking reproductive clock. Men’s sperm quality seems to deteriorate after the age of 35. The proportion of sperm carrying an X chromosome also seems to increase, meaning older dads are more likely to have daughters.
It’s common to hear men boast that at any age, they can still have children. Well, this is very correct; but researchers are warning that once men hit age 35, it is harder for them to father male children.
In a culture like ours where having a male child is considered an evidence of virility, this is a blow below the belt. The scientists also submit that by the time a man is 35 years old, the quality of his sperm would have decreased seriously.
In other words, it’s not just women who have to worry about their ticking reproductive clock.
“Men’s sperm quality seems to deteriorate after the age of 35,” a report published in the peer-reviewed journal, New Scientist, cautions.
The scientists also note that at the age of 35, the proportion of sperm carrying an X chromosome also seems to increase, meaning older dads are more likely to have daughters.
In human reproduction, the Y chromosome is responsible for making a male child.
The scientists confirm that it has been controversial as to whether the quality and quantity of a man’s sperm deteriorate with age.
“However, there is fairly convincing epidemiological evidence that older men do find it harder to conceive a child – regardless of female age – and as men get older, their partners are at increased risk of miscarriage,” says Allan Pacey, a fertility specialist at the University of Sheffield, UK.
“There is also a slightly increased risk of older men fathering children with genetic disorders,” Pacey says.
To investigate, Bronte Stone at Reproductive Technology Laboratories in Los Angeles and his colleagues analysed sperm samples from 5,081 men aged between 16 and 72. They found a deterioration in sperm quality and quantity after age 35.
Some previous studies had suggested that the decline doesn’t start until around five years later.
“Whether it’s 35 or 40, the message from this and other papers is that men should be aware of age-related changes in their reproductive system; and if they wish to become fathers, they shouldn’t leave it too late,” Pacey says.
The study also found a decrease in the ratio of Y to X-bearing sperm once men hit 55, though it is not clear why.