A new study says that old dads‘ sperm could account for as many as 30% of autism cases, and increased risk of other diseases, included schizophrenia. This is important in the field of autism research, certainly, but it also indicates that men’s “eggs”–i.e. their sperm–are not totally immune to the sands of time. Obviously, increased autism and schizophrenia rates aren’t cause for celebration, but admit it: A tiny voice in the back of your mind is cheering for the fact that women might not be the only ones who have to worry about a biological clock, after all.
The fact that fathers’ age correlates with higher incidence of disease, including autism and schizophrenia, has been observed in previous studies. But this one, conducted by deCode Genetics Inc in Reykjavik, Iceland, was the first to analyze genetic code in an effort to find out why. They found, essentially, that older fathers passed on more “new DNA variations” (i.e. mutations) than younger fathers, which is likely responsible for the difference in disease rates. On average, they found that every year a dad waits to have kids, he passes on two extra mutations.
Alexey Kondrashov, a study author and professor of evolutionary biology at the University of Michigan in Ann Arbor, said that their findings could be particularly illuminating in the case of autism:
[It may be] reasonable to assume that the ongoing increase in the incidence and prevalence of autism in many human populations could be due, at least in part, to the accumulation of mutations resulting from relaxed selection and a higher average paternal age — and not only to better recognition of cases.
He also said that, if their study findings are correct, this could be good reason for young men to store their sperm in a sperm bank for later use…which has long been the recommendation for women who choose to have children later in life.
It may seem like a paranoid precaution, but the study’s findings suggest that sperm may be more responsible for disease risk than eggs. While the mutations could be caused by environmental factors, like exposure to radiation, it’s also likely that at least some is caused by cell splitting–something that sperm do far more than eggs. (In fact, eggs don’t split at all during a woman’s reproductive years; men’s sperm split throughout their entire post-puberty lives.)
The researchers are still waiting to investigate other genetic factors to really confirm the direct ties between paternal age and autism risk, but this study is huge for the increasing number of men and women who choose to wait to reproduce.
In short: Biological clocks for all! …for better or worse.
Photo: flickr user SeedKeeper