Researchers found both lower sperm concentrations and fewer sperm that were able to swim when studying men an average of 100 days after COVID-19 infection, which is enough time for new sperm to be produced.
“There have been previous studies that show semen quality is affected in the short term following a COVID infection but, as far as we are aware, none that have followed men for a longer period of time,” said researcher Rocio Núñez-Calonge, scientific advisor at UR International Group at the Scientific Reproduction Unit in Madrid, Spain.
“We assumed that semen quality would improve once new sperm were being generated, but this was not the case. We do not know how long it might take for semen quality to be restored and it may be the case that COVID has caused permanent damage, even in men who suffered only a mild infection,” Núñez-Calonge added.
Núñez-Calonge and her colleagues decided to study this after observing that in some men attending clinics in Spain for assisted reproduction treatment, semen quality was worse after COVID-19 infection than before the infection, even though they had recovered and the infection was mild.
“Since it takes approximately 78 days to create new sperm, it seemed appropriate to evaluate semen quality at least three months after recovery from COVID,” she said.
The research team recruited 45 men with an average age of 31 at six reproductive clinics in Spain between February 2020 and October 2022. All had a confirmed diagnosis of mild COVID. The clinics had data from analysis of semen samples taken before the men were infected.
The men had another semen sample taken between 17 and 516 days after infection.
The researchers analyzed all the samples taken up to 100 days after infection, and then analyzed a subset of samples taken more than 100 days later.
They found statistically significant differences in a number of metrics, including semen volume, which was down 20%, and sperm concentration, which was down 26.5%. They also found a drop in sperm count, down 37.5%, and total motility, which is being able to move and swim forward, down 9%. Numbers of live sperm were also down 5%.
Motility and the total sperm count were the most severely affected. Half of the men had total sperm counts that were 57% lower after COVID compared to their pre-COVID samples, the study discovered. The shape of the sperm was not significantly affected.
Sperm concentration and motility had still not improved over time in the later samples analyzed.
The findings were presented Monday at the European Society of Human Reproduction and Embryology annual meeting, in Copenhagen. Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.
“The continuing effect of COVID infection on semen quality in this later period may be caused by permanent damage due to the virus, even in mild infection. We believe clinicians should be aware of the damaging effects of SARS-CoV-2 virus on male fertility. It is particularly interesting that this decrease in semen quality occurs in patients with mild COVID infection, which means that the virus can affect male fertility without the men showing any clinical symptoms of the disease,” Núñez-Calonge said in a meeting news release.
Inflammation damage to the immune system may play a role, Núñez-Calonge said.
“The inflammatory process can destroy germ cells by infiltrating the white blood cells involved in the immune system, and reduce testosterone levels by affecting the interstitial cells that produce the male hormone,” she said.
“It should be mentioned that impairment of semen parameters may not be due to a direct effect of the SARS-CoV-2 virus. There are likely to be additional factors that contribute to long-term sperm parameters decrease, but whose identity is currently unknown,” she added. “Furthermore, we did not measure hormonal levels in this study: Intense changes in testosterone, a key player involved in male reproductive health, has previously been reported in COVID-infected male patients.”
The U.S. Centers for Disease Control and Prevention has more on COVID-19 and fertility.
SOURCE: European Society of Human Reproduction and Embryology, news release, June 26, 2023
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