The human race is gradually becoming infertile with the sperm count decline by over 50 per cent over the last 50 years, an updated medical literature review with date from Central and South America, Asia and Africa shows.
If the findings are confirmed and the decline continues, it could have important implications for human reproduction.
Researchers say it would also be a harbinger of declining health in men in general since semen quality can be an important marker of overall health.
The review and its conclusions, have sparked a debate among experts in male fertility. Some say the findings are real and urgent, but others say they are not convinced by the data because the methods of counting sperm have changed so much over time that it’s not possible to compare historical and modern numbers.
The new analysis updates a review published in 2017 and for the first time includes new data from Central and South America, Asia and Africa. It was published in the journal Human Reproduction Update.
An international team of researchers combed through nearly 3,000 studies that recorded men’s sperm counts and were published between 2014 and 2020, years that had not been included in their previous analysis.
The researchers excluded studies that featured only men who were being evaluated for infertility, those that selected only men who had normal sperm counts and those whose study participants were selected based on genital abnormalities or diseases. They included only studies published in English, those with 10 or more men and those with participants whose sperm was collected in a typical way and counted using a device called a hemocytometer.
In the end, just 38 studies met their criteria. They added these to studies included in their previous review and extracted their data, which was fed into models.
Overall, the researchers determined that sperm counts fell by slightly more than 1% per year between 1973 and 2018. The study concluded that globally, the average sperm count had fallen 52 per cent by 2018.
When the study researchers restricted their analysis to certain years, they found that the decline in sperm counts seemed to be accelerating, from an average of 1.16% per year after 1973 to 2.64 per cent per year after 2020.
On a population level, the average sperm count dropped from 104 million to 49 million per millilitre from 1973 through 2019. Normal sperm counts are considered to be over 40 million per millilitre.
The study authors say they didn’t have enough data from different regions to be able to tell whether some countries had lower average sperm counts than others or whether sperm counts were declining faster in certain areas. Data from 53 countries were included in the review.
