In 2017, scientists reported that sperm counts in industrialized countries had halved in the course of just four decades. Today, they continue to decline. A new study, published in the journal Andrology, is the first to assess nationwide semen quality in Switzerland, finding that the country has one of the worst average sperm counts in Europe.
A team of scientists from the University of Geneva assessed the sperm quality of 2,523 young Swiss men aged 18 to 22 who had been recruited into the army. The group included representatives from every canton in Switzerland, creating a nationwide sample of volunteers.
The researchers focused on three key indicators of semen quality, the number, motility, and morphology of sperm cells.
In Europe, median sperm count ranges from 41 to 67 million per milliliter (ml), depending on country. According to the World Health Organization (WHO), a sperm count of below 15 million per ml makes a man subfertile. The researchers found that their cohort had a median sperm count of 47 million per ml, placing Switzerland at the bottom of Europe’s sperm league alongside Germany, Denmark, and Norway. Meanwhile, 17 percent of participants had sperm counts below 15 million per ml.
"It's important to understand that the time needed to conceive increases significantly if a man has a sperm concentration below 40 million sperm per ml," said Serge Nef, a professor in the Department of Genetic Medicine and Development at Geneva’s Faculty of Medicine, in a statement.
What’s more, in a quarter of the men studied, less than 40 percent of sperm cells were motile, and 43 percent of men had less than 4 percent normally formed sperm. Overall, only 38 percent of Swiss men had sperm concentration, motility, and morphology values that met the WHO’s criteria for healthy sperm.
"Low semen parameter values can reflect a men's fertility, when a combination of values are low, a man's ability to conceive is at risk," noted lead author Rita Rahban, a researcher in Geneva’s Department of Genetic Medicine and Development.
So why has sperm quality dropped so low? The answer to that is currently unclear but there are a few factors that may play a role. For example, the researchers found that men with poor fertility were more likely to have mothers who smoked while they were pregnant. Other factors thought to be linked to low sperm counts include drinking alcohol, obesity, stress, and pesticide exposure.
As well as impacting a man’s ability to have children, poor sperm quality has also been linked to higher incidences of testicular cancer. Analyzing data on testicular cancer prevalence in Switzerland, the researchers found that incidence of the disease has been on the up over the past few decades, rising from 7.6 cases per 100,000 men in 1980 to 10.4 in 2014.
"For 35 years, testicular cancer has grown steadily to over 10 cases per 100,000 men, which is very high compared to other European countries,” said Nef. “Sperm quality is generally lower in countries where the incidence of testicular cancer is high."
Countries with better sperm counts, like Spain, Finland, and Estonia, have lower rates of testicular cancer. The researchers believe this trend may have something to do with changes to testicular development in the womb and plan to investigate this intriguing relationship further.