Does the male biological clock really exist?

There has been much talk about male infertility recently, thanks to figures revealing the global sperm concentration has halved in the last 40 years.

It's fair to say it's a growing problem with male factor issues now contributing up to 50% of all infertility cases and male infertility impacted around 7% of all men.

While the conversation usually revolves around the ticking of a woman’s "biological clock", the number of healthy sperm a man produces does actually decline over 40 — and there are signs that might be speeding up.

Recent analysis of data from 53 countries, published in the journal Human Reproduction Update, has revealed that the rate of decline in sperm counts seems to be increasing, with sperm concentrations falling by 1.16% a year between 1972 and 2000, but 2.64% after that.

It seems, therefore, that men could have a biological clock too.

Is there really a male biological clock?

According to Mina Stanisavljevic, molecular biologist, and product research and developer at OptimallyMe says the male biological clock does exist.

"The concept of a male biological clock refers to the changes in male fertility and the genetic quality of sperm associated with ageing," she explains. "This clock suggests that, just like women, men also experience a decline in reproductive potential as they age, although the process may be more gradual."

Stanisavljevic says this decline can impact hormone levels, sperm quality, and the genetic health of offspring.

"Female fertility experiences a more distinct and noticeable decline, primarily due to menopause, which marks the end of a woman's reproductive years" she continues.

The quality and quantity of a woman's eggs diminish significantly as she approaches menopause, leading to a rapid decline in fertility, but in contrast, the decline in male fertility is more gradual.

"Men do not undergo a clear-cut biological event like menopause," Stanisavljevic continues. "Instead, there's a slow but steady decline in sperm quality and quantity.

"This includes factors like reduced sperm motility, decreased semen volume, and increased DNA fragmentation in sperm. There's also a gradual decrease in testosterone levels, but this doesn’t halt the ability to father children completely."

The male biological clock has historically received less attention than the female biological clock, which according to Stanisavljevic could be due to social perceptions and a lack of awareness about the impact of male age on reproductive outcomes.

"The effects of ageing on male fertility are also gradual and less immediately evident, which may contribute to less public and academic discussion," she adds.

How does the male biological clock work?

The male biological clock affects fertility in several ways.

"As men age, there can be a decrease in semen volume, sperm motility (the ability of sperm to move efficiently), and the percentage of normal sperm," Stanisavljevic explains. "Additionally, older age in men is associated with increased risks of genetic abnormalities in offspring, possibly due to DNA damage in sperm cells. This damage may be the result of increased oxidative stress or aberrations in the apoptosis process."

The World Health Organisation (WHO) standards state that normal semen volume ranges from 1.5 to 5 millilitres per ejaculation.

"In older men, semen volume can decrease, but it varies in how significantly this change affects individuals," Stanisavljevic continues. "Age-related changes in the prostate and seminal vesicles, which contribute to semen production, can lead to a decrease in semen volume."

Normal sperm motility, according to WHO guidelines, means that at least 40% of the sperm in a semen sample are moving.

Stanisavljevic says this includes both progressively motile sperm (those moving mostly forward) and non-progressively motile sperm (those not moving forward effectively or moving in circles).

"As men age, sperm motility can decrease," she continues. "This decline in motility can affect the sperm's ability to reach and fertilise an egg, potentially impacting fertility."

The percentage of normal sperm, also known as sperm morphology, is typically considered normal if at least 4% of sperm in the sample have a normal shape and structure.

"With ageing, there can be a decrease in the percentage of normal sperm," Stanisavljevic continues. "This change is linked to various factors, including DNA damage and oxidative stress, which can affect the sperm's structure and function."

Symptoms of male infertility

Unlike the more apparent signs of declining fertility in women, such as menopause, changes in male fertility can be less obvious.

"Some men may experience symptoms like a decrease in libido or erectile dysfunction, but these are not definitive indicators of reduced fertility," Stanisavljevic explains.

But there are medical tests to determine male fertility including:

• Semen analysis: The most common test for assessing male fertility. It evaluates various aspects of the semen and sperm, such as the volume of semen, the concentration of sperm in the semen, the percentage of moving sperm (motility), and the shape of the sperm (morphology). This test can reveal issues like low sperm count, poor sperm movement, or abnormal sperm shape.

• Hormone testing: Blood tests can check levels of hormones that are key to the reproductive process, such as testosterone and follicle-stimulating hormone (FSH). Imbalances in these hormones can affect sperm production and overall fertility.

• Imaging testing: Tests like ultrasound can be used to look for structural problems in the reproductive organs, such as blockages in the sperm delivery system.

• Post-ejaculation urinalysis: Determines whether sperm are travelling backward into the bladder instead of out the penis during ejaculation, a condition known as retrograde ejaculation.

• Specialised sperm function tests: Assess how well sperm can survive after ejaculation, attach to and penetrate an egg, and whether there are issues with the sperm's DNA integrity.

Risk factors of male infertility

According to Stanisavljevic several lifestyle habits can significantly impact male fertility including:

• A diet lacking in essential nutrients or high in processed foods may negatively impact sperm quality.

• Excessive alcohol intake can reduce testosterone levels, sperm count, and sperm quality.

• Smoking has been linked to reduced sperm count and motility, as well as DNA damage in sperm.

• Recreational drugs like marijuana and cocaine can also negatively affect sperm production and overall fertility.

• Being overweight or obese can have a detrimental effect on sperm count and motility. Similarly, being underweight can also negatively impact sperm production.

• Chronic stress can interfere with hormones needed for sperm production.

• Regular moderate exercise is beneficial, but excessive exercise can lead to decreased sperm count and quality due to its impact on hormone levels.

• Prolonged exposure to heat (like in saunas or hot tubs) can raise body temperature and adversely affect sperm production.

• Using a laptop on your lap for extended periods can generate heat and may impact sperm production.

Infertility: Read more

• Most searched-for fertility questions answered by a doctor (Yahoo Life UK, 5-min read)

• What is unexplained infertility? Doctors say quarter of Brits struggling with fertility have it (Yahoo Life UK, 5-min read)

• Six STIs that could impact fertility (Yahoo Life UK, 5-min read)

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