Sperm counts and concentrations have been declining worldwide since the 1970s, but implications for fertility are unknown: study

Researchers are sounding the alarm that declining sperm counts “threaten humanity’s survival” — but experts remain cautious about the results of a new study.

A controversial article recently published in the journal Human Reproduction Update noted that global sperm counts have dropped by about half since the 1970s — and the trend has accelerated since the year 2000.

“It is the first study to examine global trends in sperm quality in recent years and the first to show declining sperm counts in men from South and Central America, Asia and Africa,” said lead author Hagai Levine, a professor at Hadassah of the Hebrew University of Jerusalem. Braun School of Public Health.

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But many experts in the scientific community remain skeptical of the findings.

“The conclusions of the Levine group – that sperm concentrations are declining worldwide and that the decline has accelerated – are not shared by many in the andrology community,” said Dr. John K. Amory, professor of medicine at the University of Washington School of Medicine in Seattle.

A doctor in blue latex gloves holds a plastic container with biological material.

A doctor in blue latex gloves holds a plastic container with biological material. “More data will be needed over time to fully understand these phenomena,” a professor of medicine told Fox News Digital.
(iStock)

“In addition, the mean sperm concentrations observed in these studies remain well within the range of values ​​believed to be consistent with normal male fertility,” said Amory.

He also said, “More data will be needed over time to fully understand these phenomena.”

What did the research reveal?

Levine’s international team from Denmark, Brazil, Spain, Israel and the United States conducted a meta-analysis, combining findings from more than 250 previous studies from 53 countries, including the United States, between 1973 and 2018.

“This meta-analysis looks at global trends in sperm concentration (SC) and total sperm concentration (TCS) between 1973 and 2018,” Levine told Fox News Digital.

The study concluded that there is a worldwide decrease in sperm concentration not only in North America, Europe and Australia, but also in South and Central America, Africa and Asia.

The current study builds on data previously published in 2017 on sperm counts in North America, Europe and Australia.

It examined another seven years of data from 2011 to 2018 to focus on regions of the world not assessed in its initial study: South and Central America, Asia and Africa.

Levine noted that the study found that global sperm concentration fell by more than half, with a 62% decrease in total sperm concentration between 1973 and 2018.

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“We found that the rate of decline increased from 1.2% per year since 1972 to 2.6% per year since 2000,” Levine noted.

“Increased data and statistical power allowed us to assess trends in the 21st century for the first time, [up to] 2018.”

The authors noted the study's limitations because they only analyzed the participants' sperm count and concentration, but not how the sperm moved or their shape.

The authors noted the study’s limitations because they only analyzed the participants’ sperm count and concentration, but not how the sperm moved or their shape.
(iStock)

The study concluded that there is a worldwide decrease in sperm concentration not only in North America, Europe and Australia, but also in South and Central America, Africa and Asia.

What does a decreasing sperm count mean?

“Sperm count is an indicator of men’s overall health, with low levels associated with an increased risk of chronic disease, testicular cancer and a shorter lifespan,” Levine told Fox News Digital.

“Over a wider range, the decline represents a global problem related to the modern environment and lifestyle, reflecting a disrupted diseased world, at least for human reproduction.”

“Luckily for us, sperm counting methods are quite simple and haven’t really changed in the last 50 years.”

However, sperm counts alone are not a good indicator of infertility because they need to be considered in the context of a couple — namely, how they interact with the egg and the female reproductive system, according to The New York Times.

Sperm also grow from stem cells in the testes, but development can take about two months, so one sperm count is just a “snapshot” in time, The Times also noted.

What is the controversy surrounding the newspaper?

The authors noted the study’s limitations because they only analyzed the participants’ sperm count and concentration, but not how the sperm moved or their shape.

These are traits that infertility specialists use to assess reproductive ability.

Researcher uses a microscope.

Researcher uses a microscope. “As [with] any research, we’re limited by the fact that we’re seeing what we’re looking at,” lead author Levine told Fox News Digital.
(iStock)

“The authors of this paper have done a very elegant meta-analysis and I have no criticism at all of the way they did it,” said Allan Pacey, a professor of andrology at the University of Sheffield in the United Kingdom.

But Pacey told Fox News Digital he is “concerned” about the quality of the data on which the study’s analysis was based.

“The quality of the meta-analysis is as good as the original data we have, as noted by Prof. Pacey,” Levine told Fox News Digital.

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“Luckily for us, sperm counting methods are quite simple and haven’t really changed in the last 50 years.”

The paper notes that “counting with a haemocytometer is the classic way of assessment [sperm count] and has been recommended by the World Health Organization in all editions of organizations semen analysis manuals.”

But Pacey said sperm counting, even with the “gold standard” technique of hemocytometry, “is really hard.”

“I believe we’ve just gotten better at it over time through the development of training and quality control programs around the world,” Pacey added.

“We can summarize that there is strong evidence of global decline, including in Latin America, Asia and Africa, but we cannot know for sure for any specific population or country.”

“I still think that’s a lot of what we’re seeing in the data.”

Levine told Fox News Digital, “Nevertheless, if [with] any study, we are limited by the fact that we see what we look at.”

“We had 41 estimates [data from studies] from the US, but only one from Israel or one from Cuba – and some countries are not represented at all,” he added.

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“So we can summarize that there is strong evidence of global decline, including in Latin America, Asia and Africa, but we can’t know for sure for any specific population or country.”

He stated that more studies are needed to monitor sperm quality and to better understand the causes of the decline.

Current world population

The study comes after a recent United Nations report noted that “the world’s population continues to grow, but the rate of growth is slowing.”

“In 2020, world population growth will fall below 1 percent per year for the first time since 1950.”

On November 15, 2022, the world’s population is estimated to be 8 billion.

“In 2020, world population growth will fall below 1 percent per year for the first time since 1950.”

Why does the sperm count decrease?

While the study did not examine the cause of the drop in sperm count, Levine suggested that our modern environment and lifestyle play a role.

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“We have previously shown that failures in [the] male reproductive system are determined by prenatal exposure to environmental chemicals and poor health behaviors in adulthood,” Levine said.

“The study should serve as a wake-up call for clinicians, researchers, governments and the public to address the diminished sperm crisis by investing in research into unknown causes and mitigating the known causes.”

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Nevertheless, Pacey remains “on the fence” about the findings.

“The problem is that the idea of ​​a decrease in sperm count has [gotten] in popular culture and so it is very difficult to have an impartial debate on the issue – even among scientists.”

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