Sperm Counts Decline Globally By More Than 50 Percent – Medical Review
A recent review of the medical literature shows that the number of human sperm seems to have dropped by more than 50% in the last 50 years.
If the findings are validated, and the trend continues, the ramifications for human reproduction could be significant.
Semen quality is a significant indicator of overall health.
Thus it would also indicate men’s worsening health, according to the researchers.
The analysis and its findings have prompted a discussion among male fertility specialists.
Others claim the data do not convince them since the procedures for counting sperm have changed so drastically over time that it is impossible to compare historical and contemporary levels.
Nearly all specialists concur that further research is required.
“I think one of the fundamental functions of any species is reproduction. So I think if there is a signal that reproduction is in decline, I think that’s a very important finding,” said Dr. Michael Eisenberg, a urologist with Stanford Medicine. The latter was not involved in the review.
There is a considerable correlation between a man’s reproductive and general health. So it could also speak to that too, that maybe we’re not as healthy as we once were,” he said.
While others agree that the review was well-executed, they are sceptical of its results.
“The way that semen analysis is done has changed over the decades. It has improved. It has become more standardized, but not perfectly,” said Dr. Alexander Pastuczak, a surgeon and assistant professor at the University of Utah School of Medicine in Salt Lake City. He was not involved in the review.
“Even if you were to take the same semen sample and run it and do a semen analysis on it in the 1960s and ’70s versus today, you’d get two different answers,” he said.
In more recent studies of sperm analysis, which rely on samples evaluated by a different technology, “you don’t observe these tendencies,” according to Pastuczak. In fact, according to several research conducted in Northern European locations, sperm counts have increased over time.
The updated review incorporates information from other nations.
The new analysis revises a 2017 review and includes, for the first time, fresh data from Central and South America, Asia, and Africa.
It was published in the Human Reproduction Update journal.
A team of international researchers went through roughly 3,000 papers that documented men’s sperm counts and were published between 2014 and 2020, years that were excluded from their earlier analysis.
The researchers didn’t look at studies where the participants were chosen because they had genital abnormalities or disorders.
Only English-language studies with at least 10 men and participants whose sperm was collected and quantified with a hemocytometer were included.
Only 38 studies matched their criteria in the end.
These studies were added to those included in their prior review, and their data was collected and incorporated into models.
Researchers think the number of sperm dropped by slightly more than 1% per year between 1973 and 2018.
The study found that the global average sperm count had decreased by 52% by 2018.
When the researchers limited their data to specific years, they discovered that the reduction in sperm counts appeared to be accelerating, from an average of 1.16 percent per year between 1973 and 2020 to 2.64 percent per year after 2020.
Dr Hagai Levine, an epidemiologist and public health researcher at the Braun School of Public Health and Community Medicine and author of the study, remarked, “It’s really remarkable that actually, the decline is increasing.”
From 1973 to 2019, the population-level average sperm count decreased from 104 million to 49 million per millilitre.
It is considered normal for sperm counts to exceed 40 million per millilitre.
Unknown causes of the decline
The authors of the study state that they lacked sufficient data from various regions to determine whether some countries had lower average sperm counts than others or whether sperm counts were falling more rapidly in certain places.
The analysis contained information from 53 nations.
The authors did not investigate potential causes of the drop. Levine responded, “It should be researched.”
Levine,, and others have identified factors related to reduced sperm counts in earlier research.
Prenatal damage to reproductive health is possible.
“We know that stress of the mother, maternal smoking and especially exposure to manmade chemicals that are in plastic, such as phthalates, disrupt the development of the male reproductive system,” Levine said.
The way of life may also have a significant effect. According to him, obesity, lack of physical activity, and diets high in ultra-processed foods may all be to blame.
The same variables that affect health, in general, are typically detrimental to the quality of sperm.
According to one expert, attempting to conduct this type of study is inevitably laden with difficulties that confound the conclusions.
The report is scientifically or statistically sound and does an excellent job of summarizing the available data in our field.
“But it’s important to recognize that that data is still very limited in how it was collected and how it was reported,” said Dr Scott Lundy, a urologist at the Cleveland Clinic. He was not involved in the research.
According to Lundy, standards and procedures for counting sperm have evolved substantially over time, making it difficult to compare contemporary counts with previous statistics.
Nonetheless, he stated that only historical data is available to the field.
“While it’s not a cause for panic, because the counts are by and large still normal, on average, there is a risk that they could become abnormal in the future, and we have to recognize that and study that further,” Lundy said.