Source: French to English Tester Published on: 2026-03-30
Source: The Conversation – France in French (3)– By Rebecca Dean, Research Fellow, Department of Biology, University of Oxford
It was known that sperm quality declines with age. New studies reveal that spermatozoa also deteriorate during periods of abstinence, which could have consequences for fertility.
In terms of reproduction, female biology is often seen as a relentless countdown. Women are indeed born with a reserve of oocytes that will last their entire life. This means that a woman’s age generally coincides with the age of her oocytes. In other words, the older a woman gets, the older her oocytes become.
Male reproduction is governed by different mechanisms. Spermatozoa are produced continuously from puberty and can be stored in the genital tract before ejaculation. In other words, a man’s age and that of hisspermatozoaare not necessarily the same. But what happens to male gametes during this waiting period?
Men wishing to procreate are often advised to observe a period of sexual abstinence of a few days before having intercourse, in order to allow an increase in the concentration of sperm in their ejaculate. It is established that abstinenceincreases sperm count, the ejaculated volume is not the only determining factor of the degree of fertility.
The results of ournew studydemonstrate that in human beings (as well as in other animal species), spermatozoa that are stored during periods of abstinence undergo a process of “senescence” and actually experience a deterioration in quality.
We already knew that male fertilitydeclines with age. Determining whether the duration of sperm storage contributes to this decline is all the more relevant in our time as sexual activity seems to bedecline, particularly among young people. Combined with the global trend of delaying parenthood, this development could further increase thedecline in fertility observed at the global level.
Stress and exhaustion
As part of our work, we havecompiled the data on the seed of nearly 55,000 menhaving participated in 115 studies published in scientific journals. Our analyses indicate that when a man abstains from ejaculating, the health of his sperm declines significantly. Their motility (sperm movement capacity) and viability decrease, while their DNA sustains more damage.
We have identified two probable causes for these phenomena. The first is oxidative stress (which can be schematically considered as a kind of biological “rust”) that accumulates in spermatozoa and can damage them. The second is energy depletion: unlike most cells, spermatozoa are extremely active but have only a limited capacity to replenish their energy reserves. In the case of prolonged storage, they simply run out of fuel…
Before providing a sperm sample intended to be analyzed, or to be used in a treatment aimed at improving fertility or an IVF (in vitro fertilization) procedurein vitro), the World Health Organization recommends aabstinence period ranging from two to seven days. However, our work suggests that shorter delays may prove preferable to optimize the sperm quality of the samples.
These observations corroborate a recent discovery according to which, in the context of an IVF procedure, ejaculation occurring less than 48 hours before the retrievalimproves treatment outcomescompared to longer periods of abstinence.
They are also in line with a hypothesis formulated by evolutionary biologists. We know that among primates, themasturbation, which leads to frequent ejaculations, improves the quality of ejaculates. This observation, viewed in perspective with our own results, suggests that male masturbation could present an adaptive advantage: it would allow the evacuation of stored and altered spermatozoa.
Sperm deterioration does not occur only when it is stored in the male body. It can also occur after mating, during storage within the female genital tract. If human spermatozoa survive onlya few daysin females, in other animal species, such as ants, bees or bats, sperm can be stored in the females’ bodies forseveral months, even several years, before being used to fertilize the eggs.
From wildlife to humans: a biological constant
In order to verify whether the alteration of sperm during storage corresponds to a universal biological pattern, we examined data from 56 studies covering 30 different animal species, including birds, bees, reptiles, and various mammals. Again, we found that sperm quality indeed declined during the storage phase. Fathers who stored their sperm before ejaculation or mothers who preserved it before fertilization produced embryos whose chances of survival were lower.
According to us, these results are not solely due to DNA degradation. It may also be that, compared to freshly produced spermatozoa, the stored spermatozoa exhibit adifferent gene expression profile(in other words, that the genes activated in them are in a different configuration).
Interestingly, sperm deteriorates at a slower rate in females than in males. This could be explained by the fact that females of various species that store sperm have developed specialized organs thatsecrete antioxidants. These substances nourish and protect the stored spermatozoa, thereby prolonging their functional lifespan.
Ultimately, whether it concerns mice or humans, spermatozoa,just like oocytes, have an “expiration date”. When their storage is excessively prolonged before fertilization, their quality deteriorates.
Many fertility disorders depend on factors beyond our control. They can result from our exposure to environmental pollutants, stress, or stem from our genetic makeup. The duration of sperm storage, on the other hand, is an easily modifiable parameter. Our work suggests that, with a view to fertilization, it could be beneficial to prioritize spermatozoa from a recent ejaculation. This simple intervention, by optimizing semen quality, could offer a substantial gain in terms of fertility.
Rebecca Dean benefits from a Daphne Jackson Fellowship funded by the NERC.
Irem Sepil benefits from funding from the BBSRC and the Royal Society.
Krish Sanghvi does not work for, advise, hold shares in, receive funds from any organization that could benefit from this article, and has declared no affiliation other than his research institution.
–ref. Frequent ejaculations would improve sperm quality, according to a new study –https://theconversation.com/frequent-ejaculations-improve-sperm-quality-according-to-a-new-study-279464