Sperm counts and concentrations have declined globally since 1970s, but fertility implications unknown: study

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

A controversial paper recently published in the journal Human Reproduction Update noted that sperm counts have halved globally since the 1970s, and the trend has accelerated since 2000.

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

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

“The findings of the Levine group, that sperm concentrations are declining globally 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. Medicine in Seattle.

A doctor wearing blue latex gloves holds a plastic container with biological material. "More data will be needed over time to fully understand these phenomena," a medical professor told Fox News Digital.

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

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

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

What did the study show?

Levine’s international team from Denmark, Brazil, Spain, Israel and the United States conducted a meta-analysis, which combined the results of 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 global decline in sperm concentration not only in North America, Europe and Australia, but also in Central and South America, Africa and Asia.

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

He examined seven more years of data from 2011 to 2018 to focus on regions of the world not reviewed in his first study: South and Central America, Asia and Africa.

Levine noted that the study found that sperm concentration globally declined 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 percent each year since 1972 to 2.6 percent each year since 2000,” Levine noted.

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

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

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

What does low 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 decreased lifespan,” Levine told Fox News Digital.

“On a larger scale, the decline means a global problem related to the modern environment and lifestyle, reflecting a sick world disrupted, at least for human reproduction.”

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

Sperm counts alone, however, are not a great indicator of infertility because they must be considered in the context of a couple, i.e. 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 testicles, but development can take about two months, so a sperm count is only 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 looked at the participants’ sperm count and concentration, but not how the sperm moved or their shape.

These are qualities that infertility specialists use to assess reproductive potential.

The researcher uses a microscope. "How [with] any study, we are limited by the fact that we see what we look at," lead author Levine told Fox News Digital.

The researcher uses a microscope. “How [with] any study, we’re limited by the fact that we see what we look 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 of the way they have done it,” said Allan Pacey, professor of andrology at the University of Sheffield in the UK.

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

“The quality of the meta-analysis is only as good as the original data we have, as Professor Pacey pointed out,” Levine told Fox News Digital.

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

The document notes that “counting by hemocytometer is the classic way to evaluate [sperm count] and has been recommended by the World Health Organization in all versions of the organizations’ semen analysis manuals.”

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

“I think we’ve simply gotten better over time because of 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 be sure for a specific population or country.”

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

Levine told Fox News Digital, “However, how [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 cannot be sure about a specific population or country.”

He stated that more studies are needed to monitor semen 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, the world population growth rate fell below 1% per year for the first time since 1950.”

As of November 15, 2022, the world population is estimated at 8 billion.

“In 2020, the world population growth rate fell below 1% per year for the first time since 1950.”

Why does the sperm count decrease?

Although the study did not examine the cause of the decline in sperm count, Levine suggested that our modern environment and lifestyle are playing a role.

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“We have previously shown that there are disturbances [the] The male reproductive system is determined by prenatal exposure to environmental chemicals as well as poor health behaviors in adulthood,” Levine said.

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

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

“The problem is that the notion of a decrease in sperm count [gotten] in popular culture and therefore it is very difficult to have an unbiased debate on the subject, even among scientists.”

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