Men have a biological clock too – and it impacts fertility sooner than you think

When we talk about a biological clock ticking, it usually means the pressure women feel to fall pregnant before a certain age. It’s linked to the decline in eggs (ova) and fertility as females age.

But sperm numbers and fertility similarly decline with age in men. When a heterosexual couple experiences fertility issues, it’s equally likely due to male and female factors. Yet the woman is usually tested first.

But this is changing. New male infertility guidelines for Australian GPs recommend the male and female partner undergo investigations at the same time.

A growing body of research highlights the role of men in infertility and how a man’s age and health matters when trying to conceive. Let’s look at the evidence.

Sperm are produced in the testes continuously from puberty, but sperm count (the average number of sperm in an ejaculate) starts to decline when a man is in his early twenties. Men over 55 have average sperm counts close to or below the threshold for infertility.

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But it’s not just the number of sperm that matters.

Sperm need to be alive, have good motility (movement or “swimming ability”) and be the correct shape to reach and fertilise an egg in the female reproductive tract.

An adequate volume of semen (sperm and seminal fluid together) is also necessary because this provides nourishment to sperm.

From around age 30, the number of sperm with good motility and correct shape, and semen volume decline, while the number of dead sperm increases. The biggest changes generally occur from around 35 years of age.

The age-dependent decline in sperm and semen affects male fertility. In studies of more than 2,000 couples, one study showed men older than 45 took five times longer to conceive than men younger than 25. Another study found the chance of falling pregnant within a year was 20 per cent lower at 45 compared to the peak at 30.

Though a sperm might have reached and fertilised an egg, if it contains genetic damage, this can also affect fertility or the baby.

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As men age, their sperm accumulate more genetic damage, including damage to DNA and chromosomes (coils of DNA that carry genes). This is because sperm stem cells replicate hundreds of times during their life. Each time a cell replicates, there is a risk of genetic damage.

Genetic damage to sperm can stop the embryo developing and result in miscarriage. This is linked to about 30 per cent higher chance of miscarriage in men older than 40 compared to those aged 25–29.

New techniques have shown chromosomal abnormalities in sperm also increase with age. These can cause birth defects and chromosomal syndromes such as Down syndrome and Klinefelter syndrome.

Several environmental and lifestyle factors also affect semen and sperm measures, and therefore fertility.

Oxidative stress (too many damaging chemicals and not enough antioxidants) disrupts sperm production and increases sperm DNA damage, and is strongly linked to male infertility.

Oxidative stress is increased by environmental toxins such as pollution, heavy metals, pesticides and some chemicals.

Oxidative stress also increases with certain lifestyle factors, including smoking, alcohol, illicit drugs, too much processed meat and sugar consumption, obesity and being sedentary.

Male infertility can also be due to medical causes such as erectile dysfunction, or issues with the male reproductive tract or blood vessels.

A varicocele (dilation of the veins that drain the testes) is one of the most common causes of male infertility, and treatable.

One or two in 100 men with infertility will not have the tubes that transport sperm from the testes to the penis, which means their semen does not contain sperm.

However, for about one in three cases of male infertility, the cause is not known.

The World Health Organization recognises the importance of addressing infertility in everyone, regardless of sex or gender.

Australia’s first male infertility guidelines support this by recommending infertility is investigated in both partners in heterosexual couples. For the male, this includes examination of the penis, scrotum and testes, and semen and blood analyses.

For the one in nine couples in Australia with fertility problems, this will help them find answers and treatment options sooner.

If you’re looking to conceive, age is a consideration but not the only factor.

For optimal sperm health, you can focus on:

Reducing unnecessary stress or pressure around falling pregnant is also important. In Australia, most pregnancies are normal and most babies are healthy, regardless of the age of the parents.