5 hours ago
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Encouraging men to have more frequent ejaculations may boost their fertility, according to researchers who found that sperm deteriorates over time as it remains in the body.
The longer men went without sex, the more their sperm showed signs of DNA damage and oxidative stress, and the more tests rated the sperm as less viable and poorer swimmers.
The work has implications for fertility clinics and suggests that if doctors want to collect the best quality sperm, men should probably not abstain from ejaculating for several days as guidelines suggest.
“In men, the negative effects we found on sperm DNA damage and oxidative damage were large-ish, so we are confident that this is a biologically meaningful and important effect,” said Dr Krish Sanghvi, a biologist at the University of Oxford and lead author on the study.
The findings emerged from a meta-analysis that combined 115 human studies involving nearly 55,000 men, and 56 studies that looked at the impact of sperm storage in 30 non-human species. In humans and other animals, sperm tended to deteriorate while it was stored in males, regardless of the male’s age.
The World Health Organization (WHO) recommends men abstain from ejaculating for two to seven days before giving sperm for fertility tests or IVF. But the guidelines were designed to obtain the highest sperm count rather than prioritising the best quality sperm.
That decision may now become more nuanced. “All we recommend is that clinicians and couples reconsider whether long abstinence is always good, because abstinence leads to deterioration in sperm quality,” Sanghvi said. Details are published in Proceedings of the Royal Society B.
“If sperm quantity is the only thing that matters for a clinic or couple, then sexual abstinence is not necessarily a bad thing,” Sanghvi said. “But usually fertilisation success will be determined not only by how many sperm there are but the quality of the sperm too, for example in IVF.”
While the Oxford study found no impact of abstinence on fertilisation rates in humans, a recent clinical trial involving 453 couples did reveal a link.
In the trial, IVF doctors compared pregnancy rates for two groups of couples. Men in the first group abstained from ejaculating for less than two days before providing sperm for the IVF treatment. Men in the second group followed the WHO recommendations and abstained for two to seven days before providing sperm. The pregnancy rate was 46% when men abstained for less than 48 hours, and only 36% in those who abstained for longer.
For couples trying to conceive naturally, somewhere between the two and seven days could make sense. Abstain for too long and the sperm might be damaged and not very mobile. Abstain too little and the sperm may not be numerous or mature enough. “For couples, our recommendation would be that longer abstinence is not always a good thing, and that a balance between quantity [and] quality needs to be struck,” Sanghvi said.
Allan Pacey, a professor of andrology at the University of Manchester, said: “There has been growing evidence in recent years that a shorter abstinence time might be beneficial when undergoing assisted reproduction such as IVF. This is because with a short abstinence time the sperm are fresher, more motile and have lower levels of DNA damage.
“The two to seven days abstinence rule is important to stick to for men undergoing semen analysis at the diagnosis stage, as it allows results to be compared over time between laboratories and against international benchmarks. But it isn’t as important when IVF treatment is actually taking place.
“For assisted reproductive technology (Art) treatments, it’s having the freshest, most healthy sperm that is probably more important. We can do IVF treatment with a low number of sperm, and even lower if we do ICSI (intracytoplasmic sperm injection), so it isn’t as necessary for men to save up their sperm in the way that we once thought.”
