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- A new study, which builds on earlier research, suggests that sperm count globally is dropping at an accelerated rate.
- The cause behind this drop is unclear, although the authors caution that their findings have broad implications for the survival of the human species.
- Some experts agree the findings are concerning, while others say that despite the accelerated decline, it's not enough to affect the human population.
Sperm counts among men worldwide are dropping at an accelerated rate, according to a large new study published this month.
The study is an update from 2017 research by the same scientists, although critics were quick to point out that the earlier study had only included North America, Europe, Australia, and New Zealand. This time, however, the new study focuses on sperm count trends among men in regions not reviewed previously, including specifically South America, Asia and Africa. Data from more than 57 000 men across 53 countries were included in the analysis. The analysis includes an additional seven years of data collection from 2011 to 2018.
READ MORE | Five surprising signs of low sperm count in men
A news release on the study explains that the data shows that men in those regions share the significant decline in sperm counts and sperm concentration, seen previously in North America, Europe and Australia.
The international research team, led by Professor Hagai Levine of the Hebrew University of Jerusalem's Hadassah Braun School of Public Health, shows an accelerated post-2000 decline in TSC and SC globally.
Said Levine:
Drop from 101m to 49m
The meta-analysis combined findings from more than 220 previous studies across 53 countries, making it the largest meta-analysis ever conducted on the topic.
Between 1973 to 2018, the sperm concentration in men (not known to be infertile) reduced by more than 51%, from 101.2 million to 49 million sperm per millilitre of semen, the new study found.
"Furthermore, data suggest that this worldwide decline is continuing in the 21st century at an accelerated pace," write the authors, whose work appears in the journal Human Reproduction Update. Overall, sperm counts are dropping at a rate of around 1.1% a year, they say. The team believes more action and research are urgently needed "to prevent further disruption of male reproductive health."
Why this decline?
It's unclear why sperm counts are falling, as the current study didn't look at the causes. But Levine said that "lifestyle choices and chemicals in the environment are adversely affecting this foetal development."
One expert told AFP the findings show that the rate of decline in sperm count has doubled since 2000. "And we genuinely don't know why," said Sarah Martins da Silva, an expert in reproductive Medicine at Scotland's University of Dundee. "Exposure to pollution, plastics, smoking, drugs, and prescribed medication, as well as lifestyle, such as obesity and poor diet, have all been suggested to be contributory factors although effects are poorly understood and ill-defined," she said.
READ MORE | Men's fertility is affected by what they eat, studies show
Speaking to USA Today, Amy Sparks, a reproductive physiologist at the University of Iowa, commented: "We can't ignore that things are changing. Lifestyles have changed. Dietary patterns certainly have changed. Through these changes, we are exposing our body to altered conditions. In response to those altered conditions, we're seeing a decrease in sperm concentration."
However, Sparks, who was not involved in the research, cautioned that sperm counts were falling, but not enough to affect the human population.
Impact on fertility
Sperm count is just one factor that affects fertility, but the speed of sperm movement, which was not measured in the study, also plays a vital role. According to Healthline, sperm health is an important factor in a couple's ability to conceive, and there are six main criteria for healthy sperm, including volume, shape and speed.
The current study showing lower sperm concentration may be alarming, but it is above the range considered "normal" by the World Health Organization, which is between 15 million and 200 million sperm per millilitre.
Other experts remain as sceptical as they were about the 2017 study.
"I remain concerned about the quality of the data in the papers that were published, particularly in the far past," on which the analysis is based, Allan Pacey of the UK's University of Sheffield told AFP. Martins da Silva, however, believed that "the numbers and consistent findings are difficult to ignore".
Levine also believes time is running out. He cautioned:
The authors say the decline reflects a global crisis related to our modern environment and lifestyle, with broad implications for the survival of the human species.
READ MORE | Problems conceiving are not just about women - male infertility is behind 1 in 3 IVF cycles
For co-author professor Shanna Swan, it's not simply about human fertility, as sperm count is also an indicator of men's health.
"The troubling declines in men's sperm concentration and total sperm counts at over 1% each year as reported in our paper are consistent with adverse trends in other men's health outcomes, such as testicular cancer, hormonal disruption, and genital birth defects, as well as declines in female reproductive health," said Swan, who is from the Icahn School of Medicine, Mount Sinai, New York. "This clearly cannot continue unchecked."
