Human sperm quality has halved in the last half century

Men are going to have trouble being fertile in just a decade if they keep up with this rate: the number of sperm per ejaculate has been dropping steadily for nearly a century.

Its concentration has also dropped to less than half that of 50 years ago, approaching the threshold of infertility.

And the rate of decline has accelerated so far this century, doubling.

These are the alarming data of a study with studies from 53 countries.

The authors of the investigation have not delved into the causes, but point to certain lifestyle habits and exposure to chemical pollutants from the fetus.

In 2017, this newspaper published an article titled

.

The study that is published this Tuesday that the problem is not only Americans, Australians and Europeans.

Then they did not have enough data from the rest of the world regions to determine the global fertility of men.

Now, the authors of that work have published a new study with records from countries on five continents.

The new research, which includes data from Latin America, Africa and Asia, shows that the decline in sperm is global.

"Now we can say that the amount of sperm has halved in the last 50 years, globally, not just that of Westerners"

Hagai Levine, Professor at the Hebrew University of Jerusalem

Hagai Levine, a professor at the Hebrew University of Jerusalem and the main author of the work, says in an email referring to the headline of the 2017 article: "Now we can say, according to the currently available data:

.”

The research he leads, published in the

, shows that the number of sperm (sperm concentration) has gone from 101 million per milliliter to 49 million per milliliter since 1973, the date of the first available studies.

The total amount has also had a marked decrease, going from 335.7 million per ejaculation to 126.6 million in 2018, the last year available.

The work shows another fact that is as disturbing as it is intriguing: the rate of decline is accelerating.

While since 1973, sperm concentration has decreased at an annual rate of 1.16%, since 2000 it has done so at a rate of 2.64%.

Looking at other years of the period, the acceleration is confirmed: since 1985, the rate was 1.31% and already in 1995, it rose to 1.90% per year.

If this trend continues, in just a decade, the number of spermatozoa could fall below the minimum threshold from which it costs more to have children.

“Men can be considered subfertile with sperm concentrations below 40 mil/ml and infertile below 15 mil/ml,” Dr. Levine said in the 2017 article.

Jaime Mendiola, co-author of the study and professor of Preventive Medicine and Public Health at the University of Murcia, says that it is this acceleration that worries them the most.

"We don't know if he's going to go further," he says.

About the causes of the global decline in sperm, everything is hypothesis.

Mendiola recalls that, without being the objective of his study, "exposure to chemicals and environmental pollutants has been pointed out as causing hormonal disruption of the hypothalamic-pituitary-gonadal axis that would interfere with sperm production."

This researcher says that in addition to bad lifestyle habits and current conditioning factors, we must look back, “to prenatal exposure;

when we are in the fetus is the critical time for testicular development.

So the crisis had been brewing for decades.

Professor Shanna Swan, from the Icahn School of Medicine at Mount Sinai (USA), recalls in a note that low sperm counts not only affect male fertility, but also have important consequences for male health in general. , and are related to other adverse tendencies, generically called testicular dysgenesis syndrome.

"The disturbing decline in sperm counts and concentration of more than 1% per year shown in our work are consistent with adverse trends in other male pathologies, such as testicular cancer, hormonal disturbances, and genital birth defects."

Mendiola adds that connections have been established between poor sperm quality and "an increase in mortality and morbidity,

The innovation director of the IVI Foundation, one of the largest assisted reproduction groups, Nicolás Garrido, values ​​the relevance of the study: "World-class experts have done it and published it in a leading journal."

The IVI group, with a presence in several countries, has first-hand data.

They published in 2019 a work with data on the sperm quality of almost 120,000 men.

“Ours are infertility problems.

So we asked ourselves a question, are men increasingly infertile?

With data from our clinics in the United States and Spain from 20 years ago, we saw that the percentage of men with no sperm has been increasing”.

And they raised a second question,

Does this have clinical relevance?

"There are different treatments depending on the severity of the problem and we have verified that assisted reproduction treatments are increasingly complex due to the lower quality of the sperm."

“We suspect that the early exposure of the embryo/fetus and the child to contaminants with hormonal activity, endocrine disruptors, has a lot to do with it”

Nicolás Olea, professor at the University of Granada

Regarding the causes, Garrido recognizes the problem to point out the culprit or culprits.

“We know that it has to do with our life habits and our exposure to pollutants, but we are not rats that can be isolated in the laboratory to find out the role of each factor, and we are exposed to many environmental factors.”

He even mentions the possible paradoxical role of fertility clinics.

“We have been helping couples to have children for 40 years, but in the case of problems of genetic origin, it is likely that by doing so we are passing the problem on to the next generation,” he says.

In any case, genetically based infertility represents a smaller percentage of the total problem.

The professor at the University of Granada, Nicolás Olea, one of those who has done the most research on sperm quality in Spain, agrees with the authors of the study and with Garrido on how complicated it is to determine the exact causes of the problem, but he has his assumptions. guilty: "We suspect that the early exposure of the embryo/fetus and the child to contaminants with hormonal activity, endocrine disruptors, has a lot to do with it."

In fact, his group has recently published several papers on the presence of endocrine disruptors in breast milk in Spain.

The downside of all this is that, as Olea, Garrido, Levine and Mendiola say, double exposure to contaminants, both in utero and in adulthood, is a complex and, now confirmed, worldwide problem.

The good news is that the same humans who created the problem can fix it.

Levine calls urgently "for global action to promote healthier environments for all species and reduce exposures and behaviors that threaten our reproductive health."

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