Humans could face a reproductive crisis if action is not taken to tackle a drop in sperm count, researchers have warned after finding the rate of decline is accelerating.
A study published in the journal Human Reproduction Update, based on 153 estimates from men who were probably unaware of their fertility, suggests that the average sperm concentration fell from an estimated 101.2m per ml to 49.0m per ml between 1973 and 2018 – a drop of 51.6%. Total sperm counts fell by 62.3% during the same period.
Research by the same team, reported in 2017, found that sperm concentration had more than halved in the last 40 years. However, at the time a lack of data for other parts of the world meant the findings were focused on a region encompassing Europe, North America, and Australia. The latest study includes more recent data from 53 countries. Declines in sperm concentration were seen not only in the region previously studied, but in Central and South America, Africa, and Asia.
Moreover, the rate of decline appears to be increasing: looking at data collected in all continents since 1972, the researchers found sperm concentrations declined by 1.16% per year. However, when they looked only at data collected since the year 2000, the decline was 2.64% per year.
“I think this is another signal that something is wrong with the globe and that we need to do something about it. So yes, I think it’s a crisis, that we [had] better tackle now, before it may reach a tipping point which may not be reversible,” said Prof Hagai Levine, first author of the research from the Hebrew University of Jerusalem.
Previous studies have suggested that fertility is compromised if sperm concentration falls below about 40m per ml. While the latest estimate is above this threshold, Levine noted that this is a mean figure, suggesting the percentage of men below this threshold will have increased.
“Such a decline clearly represents a decline in the capacity of the population to reproduce,” he said. While the study accounted for factors including age and how long men had gone without ejaculation and excluded men known to suffer from infertility, it has limitations, including that it did not look at other markers of sperm quality.
Allan 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 over whether there is a decline.
“Counting sperm, even with the gold standard technique of [the laboratory process] haemocytometry, is really difficult,” he said. “I believe that over time we have simply got better at it because of the development of training and quality control programs around the world. I still think this is much of what we are seeing in the data.” However, Levine dismissed such concerns, adding that, in any case, the decline has been more pronounced in more recent years. (SOURCE)
