If you are a woman, you are familiar with all the pressures and challenges attached to your reproductive system. Especially in particular, your biological clock and the increasing risks to your health and your childs developmental health the later in life you decide to have kids.
However, I was surprised to learn recently that now they have now discovered a link between older fathers and a risk of Autism and Schizophrenia in children. It has been shown that older men are more likely to have children with autism or schizophrenia than younger ones. This is due to the fact that older fathers pass on significantly more random genetic mutations onto their children increasing the risk of their children having these conditions.
Interestingly enough, when comparing the mothers’ genetic contributions to the child (older mothers are more likely to have children with chromosomal abnormalities resulting in disorders such as Down Syndrome), fathers were found to be responsible for nearly all of the child’s random genetic mutations. Studies have found that a fathers age at conception accounts for 97% of new mutations found in offspring. These new or de novo mutations occur spontaneously in the egg or the sperm and are usually harmless. Most people have them.
A 20 year old father passes on an average of 25 new genetic mutations to his child whilst a 40 year old father passes 65. For each additional year in the father’s age, children gained two new mutations in their DNA, resulting in a doubling of the de novo mutation rate for every 16.5 years of paternal age. A mother however transmits about 15 new mutations, regardless of age. This makes sense due to the fact that women are born with a finite number of eggs which only undergo cell division when they mature in the ovaries, whereas men’s sperm is made constantly during their lifetime. The older he is, the more his reproductive cells have continuously divided to generate new material sometimes under environmental exposures such as radiation or other chemical influences that can affect the accuracy with which DNA is replicated.
The study involved the sequencing of the full genomes (The complete set of genetic material of an organism)of 78 trios of mother, father and child, in which the children were affected by either autism or schizophrenia but their parents had no mental disorder. The analysis showed that while paternal age had a statistically significant effect on mutation rates in children, maternal age did not.
It is thought that the study could offer a part explanation as to why the rates of autism and schizophrenia have been rising over the years. But while new genetic mutations associated with a father’s age may account for 15% or more of cases of autism, it is thought that at least half of the risk is believed to be due to inherited genes, along with other possible environmental exposures.
It’s definitely a fascinating discovery. Maybe it’s time the men to also feel the weight of age and reproduction, so all you men out there who are comfortable with “waiting until you’re 40” to have children, take note. The biological clock ticks for you too, sorry to break it to you 🙂