Evidence is mounting that male reproductive health is on the decline and an international group of experts has called for urgent action. Their report highlights the need for greater understanding of the causes of male infertility and how to better diagnose, treat and prevent it.
Lead author Moira O’Bryan, dean of science at the University of Melbourne, says compelling data shows human sperm counts and quality are dropping. One recent review found that sperm counts have fallen by more than 50% in the past 50 years.
It’s believed that increased use of endocrine-disrupting chemicals is playing a role. These chemicals, which mimic, block or otherwise interfere with hormones in our bodies, are found in everything from pesticides and household chemicals to cosmetics and have been linked to a range of health problems.
A number of animal studies have associated exposure to endocrine-disrupting chemicals with a decline in sperm quality and quantity, as well as increased DNA damage in sperm. With humans, it is more difficult to draw a conclusion about how great a contribution these chemicals are making to male infertility.
“It is complicated as there are other factors,” says O’Bryan. “We know, for example, that some medications dampen down fertility. Humans also smoke, drink alcohol and wait until they’re 45 to try to have children. There are probably genetic factors as well.”
The World Health Organisation estimates that infertility now affects one in six couples of reproductive age. About half the time it originates from the male.
Men are diagnosed as infertile based on their family history, a physical examination, hormone profiles and semen analysis. Sperm is checked for its ability to move efficiently, as well as its shape and size, and how many there are in a sample. For many infertile men, even when a problem is identified, the precise cause is unknown and few targeted treatments exist.
In the report, published in Nature Reviews Urology, the panel of leading scientists makes 10 recommendations. These include establishing a global biobank of tissues and clinical data from fertile and infertile men, their partners and children with the aim of helping researchers better understand the genetic and environmental causes of infertility.
They are also calling for genomic sequencing and rigorous testing on the impacts of endocrine-disrupting compounds on men and boys.
Considerably more is known about the female reproductive system than the male, says O’Bryan. “If we can understand more about why those sperm aren’t moving, for instance, we might be able to develop treatments to improve natural fertility.”
There is also a need for the public and clinicians to have greater awareness of the importance of male fertility. Currently, there isn’t enough emphasis on it in medical training, she says, and many doctors aren’t properly equipped to assess it. “If we can increase understanding that male infertility is common and needs to be taken seriously, then everything would flow from there – the research funding and drug development,” she believes.
Traditionally, it has been women who are encouraged to be aware of declining fertility and ticking biological clocks. But there are two players in the game and men also have biological clocks – one study from Monash University showed that, even if a man partners with a younger woman, the chance of conceiving halves in men over 50 compared with those under 40.
Many aspects of a man’s lifestyle affect sperm, from smoking and vaping to body weight. Heat has long been known to cause problems. The scrotum and testicles hang outside the body because sperm need to be a few degrees cooler than the core body temperature. If a man wears tight underwear, cycles a lot wearing Lycra or takes hot spas, it raises the testicle temperature, potentially causing a problem. Heatwaves have also been shown to damage sperm, so there are concerns that climate change may negatively affect male fertility.
There is a strong link between a man’s reproductive health and his overall health. Men diagnosed as infertile are also more likely to have diabetes and heart disease, as well as to abuse drugs and alcohol.
“The healthier you are, the healthier your sperm are likely to be,” says O’Bryan.
