Humans could face a reproductive crisis if measures are not taken to stem the decline in sperm count, researchers warn, as the rate of decline continues to accelerate.
Study Published in the journal Human Reproduction Update, based on 153 estimates from men who may not have been aware of their fertility, suggests that the average sperm concentration dropped from an estimated 101.2m per ml to 49.0m per ml between 1973 and 2018 – a drop of 51.6%. Total sperm count decreased by 62.3% during the same period.
The same team did the researchreported in 2017, found that sperm concentration More than half in the last 40 years. However, the lack of data for other parts of the world at the time meant that the findings focused on a region that included Europe, North America and Australia. The latest study includes recent data from 53 countries.
A decrease in sperm concentration was observed not only in the previously studied regions, but also in Central and South America, Africa and Asia.
Furthermore, the rate of decline appears to be increasing: Looking at data collected across all continents since 1972, the researchers found that sperm concentration has decreased by 1.16% per year. However, when they looked at data collected only since 2000, the decline was 2.64% per year.
“I think this is another sign that something is wrong with the world and we need to do something about it. So yes, I think it’s a crisis, that we [had] The first author of the research, Professor Hagai Levin of the Hebrew University of Jerusalem, said it’s best to deal with it now, before it reaches a tipping point that is irreversible.
Previous studies have suggested that fertility is compromised if the sperm concentration falls below 40m per ml. While the latest estimates are above this threshold, Levin noted that this is an average figure, suggesting that the percentage of men below this threshold may have increased.
“Such a decline clearly reflects a decline in the population’s ability to reproduce,” he said.
Although the study included factors including age and length of time a man had gone without ejaculation, and excluded men with infertility, it has some limitations, including not looking at other markers of sperm quality.
Alan Pacey, professor of andrology at the University of Sheffield, who was not involved in the work, praised the analysis, but said he remained on the fence about whether there had been a decline.
“Counting sperm, even with the gold standard technique [the laboratory process] Hemocytometry, is really difficult,” he said. “I believe we’ve gotten better at it over time with the development of training and quality control programs around the world. I still think that’s a lot of what we’re seeing in the data. “
However, Levine dismissed such concerns, adding that, in any case, the decline has become more pronounced in recent years.
Although it is unclear what may be behind the apparent trend, one hypothesis is that endocrine-disrupting chemicals or other Environmental factors May play a role, acting on the fetus in utero. Experts say factors such as smoking, drinking, obesity and poor diet can also play a role, and a healthy lifestyle can help boost sperm count.
Tina Kold Jensen of the University of Southern Denmark said the new study repeated a related trend. “No matter how many studies you include, you keep finding the same trends – that’s a little scary to me,” she said.
Professor Richard Sharpe, an expert in male reproductive health at the University of Edinburgh, said the new data showed the trend was a worldwide phenomenon.
Sharpe said the decline could mean couples are taking longer to conceive, and time is not on their side for many because they are delaying trying to conceive until a woman is in her 30s or 40s, when her fertility is already declining.
“The important point that needs to be made is that this is very bad news for couples’ fertility,” he said.
But, Sharpe said, “these issues are not just problems for couples trying to have children. They are also a major problem for society over the next 50-odd years as fewer and fewer young people will work and support the growing turnover of older people.