Fertility rates around the world have declined about 50% in the past 70 years, according to the World Economic Forum. And while much of that decline can be explained by shifting societal and economic conditions, there’s a lot to be said for how our bodies are changing too. For instance, sperm counts in men have also dropped by 50% in as many years – a rate that’s more than doubled since the turn of the 21st century. For the longest time, scientists didn’t know what was causing it. However, new research may finally explain why sperm counts are declining.
Researchers from Semmelweis University in Hungary analyzed data compiled from 27,000 studies in an attempt to uncover why sperm cells are deteriorating at an unprecedented rate. The result? Pollution, smoking, age, and particular health conditions are mostly at fault, according to findings published in the journal Reproductive Biology and Endocrinology.
Dr. Zsolt Kopa, head of the Andrology Centre at the Department of Urology at Semmelweis University, explained that “DNA fragmentation analysis” is the only scientifically sound way to test whether or not sperm is functional.
“It examines their DNA content, namely the proportion of intact or fragmented genetic material in the sperm. The more fragmented the DNA, the less the sperm’s ability to fertilize; also, it can increase the risk of miscarriage,” he explained.
From their research and data analysis efforts, they confirmed that healthy sperm counts are declining for reasons that aren’t all that surprising. However, the one discovery that was illuminating was that age doesn’t have quite as big of an effect on sperm health as previously thought.
Sperm counts are declining for very particular reasons
“Based on previous research, we expected that the quality of sperm cells starts to deteriorate significantly after age 40, but our meta-analysis suggests that this age could be much higher,” said Dr. Anett Szabó, a Ph.D. student and first author of the study. “But, of course, this is not to say that it’s worth waiting to start a family as other important parameters can also deteriorate with advancing age.”
They also found that smoking can increase sperm deterioration by 9.19% on average compared to non-smokers. However, alcohol consumption and body weight showed no significant impact.
Pollution, however, certainly did. Air pollution and exposure to chemicals such as insecticides and pesticides raised DNA fragmentation rates by 9.68% on average. (Related: Penis size is shrinking due to environmental pollution, scientist warns)
Finally, health conditions including varicocele, or vein dilation in the spermatic cord, increased sperm deterioration by 13.62% on average. Glucose intolerance had a similar effect. Other health conditions like tumors and bacterial STIs were also pinpointed.
“DNA fragmentation can be of outstanding importance, and the test was officially included in the international guidelines in 2021. However, there are still no official standards on the values of infertility and fertility,” said Dr. Kopa.
“In clinical practice, we use only consensus values. Generally, a fragmentation below 25% can be considered optimal; above this, the chance of spontaneous conception decreases. Beyond 50%, the success rate of IVF is also lower.”
