- Over the past 50 years, human sperm counts appear to have fallen by more than 50% around the globe.
- It could have important implications for human reproduction.
- Researchers say it would also be a harbinger of declining health in men in general.
The review, and conclusions of recent findings, 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. 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% by 2018.
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 was included in the review. The authors also didn’t look at what might be causing the decline. “It should be studied,” Levine said. “We know that stress of the mother, maternal smoking and especially exposure to man made chemicals that are in plastic, such as phthalates, disrupt the development of the male reproductive system,” he added.
Lifestyle may also play an important role. Obesity, a lack of physical activity and diets high in ultra processed food may all be culprits. One expert said that, ultimately, trying to do this kind of study is fraught with problems that complicate the findings. “The paper is very scientifically or statistically robust and does a good job of summarizing the data that is available in our field. But it’s important to recognize that that data is still very limited in how it was collected and how it was reported,” said Dr. Scott Lundy, a urologist at the Cleveland Clinic.
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