Has Sperm Count Dropped that much in the last 50 years?

According to an updated study of medical literature, human sperm counts appear to have decreased globally over the past 50 years by more than 50%.

The discoveries could have significant consequences for human reproduction if the reduction persists and the findings are validated. Since semen quality can be a significant indicator of general health, researchers think it would also be a sign of men's overall health declining.

The review and its findings have sparked discussion among male fertility specialists. Some claim the findings are accurate and urgent, but others claim the data does not convince them because it is impossible to compare historical and contemporary counts because sperm counting techniques have changed so much over time.

Nearly all experts agree that the issue needs more study.

“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 who was not involved in the review.

“There is a strong link between a man’s reproductive health and his overall health. So it could also speak to that too, that maybe we’re not as healthy as we once were,” he said.

Some claim that the review was well-done, although they disagree with its conclusions.

“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.

According to Pastuczak, "you don't see these trends" in more recent studies of semen analysis that use samples examined in a different way. In fact, he claimed, certain research in Northern European countries reveal rising, rather than falling, sperm counts with time.

New data from Central and South America, Asia, and Africa are included in the new analysis for the first time, which also updates an evaluation that was released in 2017. It was printed in the Human Reproduction Update journal.

Almost 3,000 studies that measured men's sperm counts that were published between 2014 and 2020, years not taken into account in their prior analysis, were searched through by an international team of experts.

The studies that only included men who were being examined for infertility, those that only included males with normal sperm counts, and those whose study participants were chosen based on genital abnormalities or disorders were all disregarded by the researchers. Only studies with 10 or more men, those published in English, and those whose participants had their sperm collected in a conventional manner and counted using a tool called a hemocytometer were considered.

Only 38 studies ultimately met their requirements. They extracted the data from these studies and added them to the studies they had previously reviewed.

Overall, the researchers found that between 1973 and 2018, sperm counts decreased by a little bit more than 1% year. The study found that by 2018, the average sperm count has decreased by 52% globally.

Researchers discovered that the decline in sperm counts appeared to be accelerating, going from an average of 1.16% per year after 1973 to 2.64% per year after 2020, when they limited their analysis to specific years.

“It’s really remarkable that actually, the decline is increasing,” said study author Dr Hagai Levine, an epidemiologist and public health researcher at the Braun School of Public Health and Community Medicine.

From 1973 to 2019, the population's average sperm count decreased from 104 million to 49 million per milliliter. Sperm counts over 40 million per milliliter are regarded as normal.