A new study shows that male sperm counts have fallen by more than 50% over the last 50 years, a troubling trend that could hinder mankind’s ability to reproduce in the future. A decline in sperm counts has implications for the health of men overall. Lower sperm counts have long been linked to an increased risk of chronic disease and a decreased lifespan.
The report, published in the journal Human Reproduction Update, combines data from 53 countries, including those from Europe, Asia, Africa, North and South America. Researchers have been collecting data on sperm counts for decades and the latest report adds another set of data, collected from 2011 to 2018, to the overall analysis, which began in 1973.
The new numbers show that the sperm count decline in North America, Europe and Australia has continued and even accelerated “alarmingly” since the year 2000.
“Overall, we’re seeing a significant worldwide decline in sperm counts of over 50 per cent in the past 46 years, a decline that has accelerated in recent years,” said co-author Hagai Levine from the Hebrew University of Jerusalem.
According to the report, the average sperm count of men worldwide was around 101 million sperm per milliliter of sperm in 1973. That number is now down to just 49 million.
Scientists believe the decline is caused by disturbances in the development of the reproductive tract during fetal life, which can lead to lifetime impairment of fertility and other reproductive dysfunctions. The authors wrote that these findings should “serve as a canary in a coal mine,” and cautioned that poor lifestyle choices and chemicals in the environment are “adversely affecting this fetal development.”
“We have a serious problem on our hands that, if not mitigated, could threaten mankind’s survival. We urgently call for global action to promote healthier environments for all species and reduce exposures and behaviors that threaten our reproductive health,” Dr Levine added.
Sperm counts can also be used as an indicator of overall health, a condition known as testicular dysgenesis syndrome.
“The troubling declines in men’s sperm concentration and total sperm counts at over 1 per cent each year as reported in our paper are consistent with adverse trends in other men’s health outcomes, such as testicular cancer, hormonal disruption, and genital birth defects, as well as declines in female reproductive health,” said Shanna Swan, another author of the study from the Icahn School of Medicine, Mount Sinai, New York.
“Data suggest that this worldwide decline is continuing in the 21st century at an accelerated pace. Research on the causes of this continuing decline and actions to prevent further disruption of male reproductive health are urgently needed,” researchers included in the study.
But the report is being taken with a grain of salt in some corners of the healthcare community. Some said they aren’t convinced with the findings because the methods of counting sperm have changed considerably over the last 50 years.
“The way that semen analysis is done has changed over the decades. It has improved. It has become more standardized, but not perfectly,” said Dr. Alexander Pastuczak, a surgeon and assistant professor at the University of Utah School of Medicine in Salt Lake City, who was not involved in the review.
“Even if you were to take the same semen sample and run it and do a semen analysis on it in the 1960s and ’70s versus today, you’d get two different answers,” he said.
But almost everyone agreed the issue needs to be studied further.
“I think one of the fundamental functions of any species is reproduction. So, I think if there is a signal that reproduction is in decline, I think that’s a very important finding,” said Dr. Michael Eisenberg, a urologist with Stanford Medicine who was also not involved in the review.
Dr. Scott Lundy, a urologist with the Cleveland Clinic, said the paper does a good job of explaining the analysis in terms that are easy to understand, but the data remains limited.
“While it’s not a cause for panic, because the counts are by and large still normal, on average, there is a risk that they could become abnormal in the future, and we have to recognize that and study that further,” Lundy said.