Male 'Biological Clock' Starts Ticking Earlier Than You Might Think

When most of us hear the phrase “biological clock”, we probably think about declining fertility rates and hormonal changes in women as they age.

But experts think this so-called clock affects men, too. 

Speaking to the BBC, Professor Allan Pacey, a male fertility expert, said men aged 40 and above are “about half as fertile” as those in their mid-20s. 

And a 2022 study found that for women aged 35-40 who were attempting to conceive, there was a “significant drop” in the live birth rate if their male partner was above 40. 

Does that mean a man’s 40th birthday marks the ticking of his “biological clock”? Here, Josephine Smith, a resident physician at Supplement Hub, shared her thoughts.

When does the male “biological clock” start ticking?

According to a study analysing over 450,000 births, there appeared to be a clear drop in male fertility beginning at ages 35 to 39.

This change stood even when researchers accounted for the female partner’s age; fertility continued to decline steadily in every age bracket after 40.

And, per an analysis of nearly 5,000 IVF cycles, men aged 51 and over were less likely to have sperm that met the World Health Organisation’s standards for healthy semen.

The same research found that generally, older men were linked to less successful pregnancies. 

“Most women have heard the phrase ‘ticking clock’ when it comes to fertility – and most 20 and 30-something women will tell you they are always questioned by family members on when they’re planning on having children,” Smith said.

“However, not enough narrative surrounds where men come into this equation. Research shows that by the mid-30s, sperm quality begins to drop, and by 40, risks associated with DNA damage increase. 

“Understanding male fertility is just as important as understanding female fertility, but that conversation just hasn’t caught up yet.” 

How can men keep sperm healthy as they age?

The mid-30s change Smith alluded to is neither universal nor unchangeable. 

Regular exercise; a healthy diet rich in fibre, protein, and antioxidants; adequate sleep; and reducing alcohol consumption can all help to keep semen healthy.

The NHS said you should consider medical help if you haven’t conceived after a year of trying, though you might want to do this sooner if you’re over 35.