The sperm count of men across the world has decreased by over 50% in the last 50 years, a new study by researchers at Hebrew University found.
Furthermore, the peer-reviewed study, led by Prof. Hagi Levin of the Hebrew University School of Public Health of and Hadassah Medical Center in Jerusalem and published in the scientific journal Human Reproduction on Tuesday, found that the rate of the decrease has increased in the 21st century.
The new study, which aims to look at trends in sperm count among men in every continent, is a follow-up to a previous study that found a 50% drop in sperm count in men from North America, Europe and Australia between 1973 and 2011.
Despite the previous study, however, the researchers noted that "too few studies have been published in South/Central America, Asia and Africa (hereafter SAA) to draw a conclusion about trends in those continents."
In the latest study, the researchers modified the database that was being used so that they could see if the same trends were occurring in men in Africa, Latin America and Asia, including in Israel.
What does sperm count indicate?
Sperm count is an indicator not only of a man's fertility but also possibly his health, noted Hebrew University. For instance, a low sperm count may indicate an increase in the risk of morbidity.
The new study accounted for over 10,000 scientific papers examining sperm quality between 1973 and 2018. After a selection process, the researchers used data from 223 studies in 53 countries in the study, then looked at sperm quality trends during this time interval, as well as after the year 2000.
"Here, we report on global trends in SC [sperm count] and TSC [total sperm count] in publications 1981 through 2019, which combines results of both searches and analyses," the researchers said. "This expanded analysis addresses two important questions. With increased sample size, was a trend seen in South America, Africa and Asia? Did the trends we reported continue post-2011?"
The results indicated a decrease of about 50% in the sperm count and total sperm count between 1973 and 2018. The research also found that sperm concentration had decreased by 52% among the general global population and that total sperm count had decreased by 62% during the entire study.
Furthermore, the most significant decrease occurred in men from North America, Europe and Australia, but a decrease also occurred in men from Asia, Africa and Latin America.
Additionally, when the researchers compared the data from before and after 2000, they found that the decline in sperm count is increasing over time.
What is causing the global decline in sperm count?
“The main suspects are global warming and air pollution, but also exposure to chemical substances and smoking before birth, and exposure to pesticides, smoking, mental stress and poor nutrition in adult life.”
Prof. Hagi Levin, Hebrew University School of Public Health and Hadassah Medical Center
Though the new study did not examine the causes of the decline, prior research indicated a link with environmental conditions and lifestyle.
"Since we are seeing a decline in sperm quality that is getting worse over the years, it is almost certain that the changing world around us has an effect on this," remarked Levin. "The main suspects are global warming and air pollution, but also exposure to chemical substances and smoking before birth, and exposure to pesticides, smoking, mental stress and poor nutrition in adult life."
"In light of the great importance of sperm counts for male fertility and human health, this study is a wake-up call for researchers, policymakers, health authorities and the public around the world and in Israel, which requires consideration and taking actions to correct the current situation," Levin added. "The reasons for the sharp and continuous decrease in sperm counts must be investigated so that we can prevent further deterioration in the years to come. We may have reached a time when we will have to offer the option of preserving quality sperm by freezing among young men, in order to ensure fertility in the future as well—just like egg freezing."