Men do not have a limit marked by nature in which a ‘stop’ is applied when it comes to having more offspring (such as if women have), although little by little it is becoming more complicated. But even if there is no such limit choosing to become parents at an older ageis not the most recommended due to the great risks it has, as pointed out a published study in Nature magazine recently.
Risk age. The idea that the age of the mother It is a crucial factor for the baby’s health is deeply rooted in the collective consciousness and has been seen to Older age is associated with diseases such as Down syndrome. However, science has been accumulating evidence for years that the father’s age also plays a fundamental role.
We already knew that about 80% of new genetic mutations (those not inherited from either parent) come from the paternal germline. What we didn’t know was the magnitude of the mechanism that accelerates it.
Selfish sperm. The team of researchers from Wellcome Sanger Institute in the United Kingdomled by Raheleh Rahbari and Matthew Neville, has put a name and surname to the problem: selfish selection of spermatogonia.
In simple terms, this means that certain genetic mutations not only alter a gene, but give a competitive advantage to the stem cells that produce sperm (spermatogonia). These mutated cells replicate faster and more efficiently than their healthy counterparts, so they will predominate ahead of the gametes that are suitable.
As a result, as the years go by, the percentage of sperm carrying these “selfish” mutations increases exponentially, not linearly, and this results in a man in his early thirties having 1 sperm in every 50 with a disease-causing mutation. But when you reach the age of 70, this figure shoots up to 1 sperm in every 20.
How it has been seen. To reach this conclusion, scientists needed highly precise technology, since right now standard sequencing methods have an error rate that can make it difficult to see a specific mutation.
This is where a technique called duplex sequencing (NanoSeq). Its operation is very simple, since instead of reading a single strand of DNA, this method reads both strands of the double helix. If a mutation is detected on both strands in exactly the same place, it is virtually impossible for it to be a machine error. It is a real mutation. Thanks to this precision, they were able to analyze more than 35,000 mutations in the sperm of 81 men between 24 and 75 years old.
In this case, the results identified more than 40 key genes where these selfish mutations tend to occur. Most are associated with serious neurodevelopmental disorders, such as autism itself or even increasing the probability of suffering from cancer throughout the offspring’s life.
Genetic sanctuary. Interestingly, the study revealed a surprising fact when comparing the mutations in the sperm with those in the blood cells of the same men. In the blood, the impact of lifestyle was evident: men who smoked, drank alcohol excessively or were obese had a much higher mutation burden.
However, no correlation with these factors was found in sperm. The mutations accumulated at a rate eight times slower and seemed immune to the individual’s habits. This suggests that the testicles function as a biological “sanctuary,” a protected niche that the body strives to keep safe from harmful environmental factors.
Family planning. Logically, when making the decision to reproduce this changes many things, since to avoid this accumulation of mutations it would be interesting to do it the younger the better. Both in the case of men and women.
But the reality we have in our society is that family conciliation has not yet been achieved, and this means that becoming mothers and fathers has to be delayed. In this way, the study points to the possibility of including sperm freezing at an earlier age if considering having children or considering genetic screening techniques for elderly parents. Although all this has a cost behind it.
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