Copenhagen, Denmark
More than three months after suffering a mild COVID infection, men have lower sperm concentrations and fewer sperm that can swim, according to new findings presented at the 39th annual meeting of the European Society for Human Health Reproduction and Embryology (ESHRE). .
Professor Rocio Núñez-Calonge, scientific advisor to UR International Group at the Scientific Reproduction Unit, Madrid, Spain, said that after an average of 100 days after SARS-CoV-2 infection, there did not appear to be an improvement in the quality and concentration of sperm. even though new sperm would have been produced at that time.
“There have been previous studies showing that semen quality is affected in the short term after a COVID infection but, to our knowledge, none have followed men for a longer period of time,” he said. “We assumed that semen quality would improve once new sperm were generated, but that was not the case. "We don’t know how long it may take for semen quality to recover and it may be the case that COVID has caused permanent damage, even in men who suffered only a mild infection."
Prof. Núñez-Calonge and his colleagues observed that in some men who attended clinics in Spain for assisted reproduction treatment, semen quality was worse after COVID infection than before infection, although they had recovered and the infection was mild. So they decided to investigate if COVID had influenced the drop in quality.
“Given that it takes approximately 78 days to create new sperm, it seemed appropriate to evaluate semen quality at least three months after recovery from COVID,” said Prof. Núñez-Calonge.
Between February 2020 and October 2022, researchers recruited 45 men attending six reproductive clinics in Spain for the study. All had a confirmed diagnosis of mild COVID and the clinics had data from analysis of semen samples taken before the men became infected. Another semen sample was taken between days 17 and 516 after infection. The median (mean) age of the men was 31 years, and the amount of time between pre- and post-COVID samples was a median of 238 days. The researchers analyzed all samples taken up to 100 days after infection and then analyzed a subset of samples taken more than 100 days later.
They found a statistically significant difference in semen volume (20% less from 2.5 to 2 milliliters), sperm concentration (26.5% less from 68 to 50 million per ml of ejaculate), sperm count (37.5% less from 160 to 100 million per milliliter of semen), total motility, that is, being able to move and swim forward (9.1% less, from 49% to 45%) and the number of live sperm (5% less, from 80% to 76%).
Prof. Núñez-Calonge said that motility and total sperm count were the most affected. Half of the men had total sperm counts that were 57% lower post-COVID compared to their pre-COVID samples. Sperm shape was not significantly affected.
When researchers looked at the group of men who provided a sample more than 100 days after COVID, they found that sperm concentration and motility had not yet improved over time .
“The continued effect of COVID infection on semen quality in this later period may be caused by permanent damage due to the virus, even in a mild infection. We believe that doctors should be aware of the harmful effects of the SARS-CoV-2 virus on male fertility. It is especially interesting that this decrease in semen quality occurs in patients with mild COVID infection, which means that the virus can affect male fertility without men presenting any clinical symptoms of the disease,” says Prof. Núñez-Calonge.
It is known that the SARS-CoV-2 virus can affect the testicles and sperm, but the mechanism is still unknown.
Prof. Núñez-Colange says the inflammation and damage to the immune system seen in long COVID patients could be involved. “The inflammatory process can destroy germ cells by infiltrating white blood cells involved in the immune system and reduce testosterone levels by affecting interstitial cells that produce the male hormone,” he said.
“It is worth mentioning that the deterioration of semen parameters may not be due to a direct effect of the SARS-CoV-2 virus. There are likely additional factors that contribute to the long-term decline in sperm parameters, but whose identity is currently unknown. Furthermore, we did not measure hormone levels in this study: intense changes in testosterone, a key factor involved in male reproductive health, have been previously reported in male patients infected with COVID.”
The researchers plan to continue studying men to measure both semen quality and hormonal status over time. They believe there should be more research on men’s reproductive functions after COVID infection to see if their fertility is temporarily or permanently affected.
The president of ESHRE, Professor Carlos Calhaz-Jorge of the Centro Hospitalario del Norte de Lisboa and the Hospital de Santa María de Lisboa (Portugal), was not involved in this research. He commented: “This is interesting research by Prof. Núñez-Calonge and her colleagues and shows the importance of long-term follow-up of fertility patients after a COVID infection, even if it is a mild infection. However, it is important to note that semen quality in these patients after a COVID infection is still within the World Health Organization criteria for "normal" semen and sperm. "Therefore, it is unclear whether these reductions in semen quality after COVID infection translate into decreased fertility and this should be the subject of further investigation."
