Sperm counts in men around the world are declining at an accelerating rate after halving in the past 40 years, a large new study announced on Tuesday, calling for action to halt the decline.
The study, led by Israeli epidemiologist Hagai Levine, updates 2017 research that had come under scrutiny to include only North America, Europe, Australia and New Zealand.
The new study includes data from more than 57,000 men collected from more than 223 studies in 53 countries, making it the largest meta-analysis ever on the subject.
Along with the additional new countries, it confirmed the 2017 finding that sperm count had halved over the past four decades.
Between 1973 and 2018, the concentration of sperm in men not known to be infertile dropped by more than 51%, from 101.2 million to 49 million sperm per milliliter of semen, according to the new study.
“Furthermore, the data suggest that this global decline is continuing into the 21st century at an accelerating rate,” said the study published in the journal. Human Reproduction Update.
Sperm count drops at a rate of about 1.1% per year, according to research.
More action and research are urgently needed “to prevent further disruption to male reproductive health”, he added.
“We really don’t know why”
Sperm count isn’t the only factor that affects fertility — the speed of sperm movement, which wasn’t measured in the study, also plays a crucial role.
And the lower sperm concentration of 49 million is still well above the range considered “normal” by the World Health Organization – between 15 million and 200 million sperm per millilitre.
Sarah Martins da Silva, a reproductive medicine expert at Scotland’s University of Dundee not involved in the study, said it showed the rate of decline in sperm count had doubled since 2000.
“And we really don’t know why,” she added.
“Exposure to pollution, plastics, smoking, drugs and prescription medications, as well as lifestyle, such as obesity and poor diet, have all been suggested to be contributing factors, although the effects are misunderstood and ill-defined.”
Other experts said the new study did not resolve their skepticism about the 2017 research.
“I remain concerned about the quality of the data in the papers that have been published, particularly in the distant past,” on which the analysis is based, Allan Pacey of Britain’s University of Sheffield told AFP.
While praising the “very elegant meta-analysis”, Pacey said he thinks we’ve “just gotten better” at the difficult task of counting sperm, which may explain the drop in rates.
But Martins da Silva dismissed criticism of the study’s findings, saying “the consistent numbers and results are hard to ignore”.
© Agence France-Presse