Doctors warned of human extinction if the number of sperm in men continues to decline at current rates.

Researchers evaluated the results of nearly 200 studies and reported that sperm counts in men from North America, Europe, Australia and New Zealand had halved in less than 40 years.

Some experts are skeptical about the results published in the Human Reproduction Update.

But chief researcher Dr. Hagai Levine said he was "very concerned" about what might happen in the future.

This assessment, one of the largest studies ever conducted, collected 185 studies between 1973 and 2011.
"If the decline continues in this direction, people will be extinct," Levine, the epidemiology professor at the BBC, told the BBC.

The rate of decline is increasing!

"If we do not change the way we live, the environment and the chemicals we are exposed to, I am very concerned about what will happen in the future."

"In the end we may have a problem with breeding in general, and may lead to the extinction of human species."

Non-participants in the study praised the quality of the research but think it is too early to reach these conclusions.

Dr. Levine of the Hebrew University of Jerusalem found a 52.4% decrease in sperm concentration and a 59.3% decrease in total sperm counts for men from North America, Europe, Australia and New Zealand.

The study also indicates that the rate of decline continues among men living in these countries and may even increase.

By contrast, no decline has been observed in South America, Asia and Africa, but researchers point out that very few studies have been conducted on these continents.

Dr Levin, however, is concerned that the number of sperm will eventually drop in these places as well.

«Imbalance» in previous studies

Many previous studies have pointed to a sharp decline in the number of sperm in developed economies, but skeptics are not correct for many of these studies.

Some of these studies have been achieved in relatively few men, or have included only the sample of men who visit fertility clinics and are, in any case, more likely to have fewer sperm.

We should also consider that studies that claim to have a lower sperm count are published in scientific journals than their non-reference counterparts.

Another difficulty we face is that the previous and old methods used to calculate the number of sperm may be overestimated in the real number.

Looking at these factors together, may be the wrong view about the low number of sperm.

But researchers claim to have explained some of these flaws, leaving skeptics such as Professor Allan Pacey of Sheffield University less skeptical.

"I was not convinced about the many studies that have been published so far, which claim that the numbers of human sperm have declined in the recent past," he said.

"However, a study by Dr. Levin and his colleagues today deals directly with many of the mistakes in previous studies."

Professor Bassey believes that although the new study has reduced the rate of error, but not completely excluded, so we have to deal with the results cautiously, he said.

"These discussions have not yet been resolved, and obviously we have a lot to do."

However, the "paper" represents a step forward and shows us which data may ultimately help us identify better studies to test this issue.

Smoking and Obesity

There is no evidence of the cause of this apparent decline. But was linked to exposure to chemicals used in pesticides, plastics, obesity, smoking, stress, diet and even watching television frequently.

Dr. Levine says it is necessary to know the cause of the decrease in the number of sperm and find ways to reverse the current.

"We should start with serious steps, for example, better regulation of human-made chemicals, and continuing efforts to reduce smoking and obesity," he said.
Sources
http://www.bbc.com/news/health-40719743

https://academic.oup.com/DocumentLibrary/humupd/PR/dmx022_final.pdf