Sperm Cell

Globally, sperm counts and concentrations have been declining since the 1970s. However, fertility implications remain unknown

Researchers have raised the alarm that decreasing sperm counts could “threaten humanity’s survival”, but experts remain cautious over the findings of a new study.

Recently, a controversial paper in Human Reproduction Update stated that global sperm count has fallen by approximately half since the 1970s. This trend has been increasing since 2000.

Hagai Levine, a professor at the Hadassah Braun School of Public Health at the Hebrew University of Jerusalem, said that the study is the first to look at global trends in semen-quality quality over recent years. It also shows declining sperm count among men from South, Central, Asia, and Africa.

However, many scientists remain skeptical about the conclusions.

Dr. John K. Amory from the University of Washington School of Medicine, Seattle said that “the conclusions of the Levine groups — that sperm concentrations worldwide are decreasing and that the decline is accelerating — are not shared”

Amory stated that the average sperm concentrations found in these studies were well within the range of values considered to be normal for men’s fertility.

He added, “More data is needed over time to fully understand these phenomena.”

What was the result of the study?

Levine’s international team, consisting of members from Israel, Brazil, Spain, and Denmark, performed a meta-analysis that combined the results from more than 250 studies done in 53 countries between 1973 and 2018.

Levine stated that “This meta-analysis examines worldwide trends in total sperm content (TCS), and

sperm concentrate (SC) between 1973-1982.”

This study draws on data published in 2017 about sperm counts in Australia, Europe, and North America.

The study examined seven years more of data between 2011 and 2018, to identify regions in the world not covered by their initial study, such as South and Central America and Asia.

Levine pointed out that global sperm levels declined by more than half in the study, with a 62% decrease in total sperm count between 1973 and 2018.

Levine observed that “the pace of decline increased from 1.2% per year since 1972 to 2.6% per year since 2000.”

“The increase in data and statistical power enabled us to evaluate trends in the 21st Century, [up until] 2018.

According to the study, there is a global decrease in sperm concentration in North America, Europe, Australia, and elsewhere in the world. This includes South and Central America as well as Africa, Asia, and Africa.

What does declining Sperm count mean?

Levine stated that men’s perm counts are an indicator of their overall health. Low levels of it can lead to an increased risk of testicular cancer, chronic disease, and shorter life expectancy.

“The decline, on a wider scale, signifies a global issue that is related to the modern environment and lifestyle. It represents a disrupted world, at minimum for human reproduction.”

However, sperm counts are not enough to determine if a couple is infertile. They need to be considered together, namely how the eggs and female reproductive tract interact, according to The New York Times.

The testes also produce sperm from stem cells, however, this process can take up to two months. The Times noted that one sperm count is only a “snapshot” of the time.

What’s the controversy about the paper?

The limitations of the study were noted by the authors. They only looked at the sperm count and

concentration, but not their movement or shape.

These are the qualities that fertility specialists use to evaluate reproductive potential.

Allan Pacey, professor of urology at the University of Sheffield in England, said that “the authors of this paper have performed a very elegant meta-analysis and I have no criticism about the way they did this.”

Pacey stated that he was “concerned about the quality” of the data used in the analysis.

Levine stated that “the quality of the meta-analysis is as good as the original data we’ve got, as noted Prof. Pacey.”

“Fortunately for us, the methods of counting sperm have not changed much in the past 50 years.”

According to the paper, counting by hemocytometer (the classic way to determine [sperm count]) is recommended by the World Health Organization in all editions of its semen analysis manuals.

Pacey however stated that it was “really difficult” to count sperm even using the “gold standard”, haemocytometry.

Pacey said, “I believe that we have just gotten better over time because of the development training and quality control programs around the globe,” Pacey stated.

“I believe this is a lot of what we see in the data.”

Levine stated, “Nevertheless, [with] any research, we are bound by the fact we see what our eyes see.”

He said, “We had 41 estimates [data from studies] from the USA, but only one from Israel and one from Cuba — some countries aren’t represented at all.”

“So, we can conclude that there is strong evidence of global decline, including in Latin America and Asia, but it’s not possible to be certain for any specific population or country.”

He said that more research is needed to monitor the quality of semen and to understand the causes of its decline.

Current world population

This study follows a United Nations report that noted that “the world’s population continues its growth, but the pace is slowing down.”

The world’s population was 8 billion as of November 15, 2022.

“In 2020, global population growth rates fell below 1 percent per annum for the first time since 1950,”

Why is sperm count declining?

Levine suggested that our modern lifestyle and environment may be contributing to sperm counts declining, even though the study didn’t examine the causes.

Levine stated, “We have shown previously that disturbances in [the] male reproduction system are caused by prenatal exposures to environmental chemicals as well as poor health behaviors in adulthood.”

“The study should be a wake-up call to clinicians, researchers, and the public. They need to address the decreased sperm supply by investing in research into unknown causes and mitigating existing causes.

Pacey is still “on the fence”, however, about the findings.

“The problem with this is that the idea of a decline in sperm count has [gotten] into popular culture, so it’s difficult to have an equal-handed discussion about the topic — even among scientists.”

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