After adjustment for the other parent's age, birth order, maternal education, and other covariates, both maternal and paternal age were independently associated with autism (adjusted odds ratio for maternal age 35 vs. 25–29 years = 1.3, 95% confidence interval: 1.1, 1.6; adjusted odds ratio for paternal age 40 years vs. 25–29 years = 1.4, 95% confidence interval: 1.1, 1.8). Firstborn offspring of 2 older parents were 3 times more likely to develop autism than were third- or later-born offspring of mothers aged 20–34 years and fathers aged <40 years (odds ratio = 3.1, 95% confidence interval: 2.0, 4.7). The increase in autism risk with both maternal and paternal age has potential implications for public health planning and investigations of autism etiology.
This differs from other studies I have posted, in that the mothers' age appears to be a risk factor, as well as the fathers' age.
We have been trying to fool Mother Nature by postponing fertility indefinitely. Women have learned to their sorrow that this is not always possible: advanced maternal age increases the risk of infertility. So it is now interesting to see that advanced paternal age can be a problem as well.
For those who are new to this blog, here is the theory: as a man ages, his "fertility" doesn't necessarily decline, in that his sperm count may be just fine. But it appears that when the DNA replicates, it does not replicate precisely. The older the man is, the greater the likelihood of small genetic defects appearing in his DNA as it replicates. When I say "small" genetic defects, I mean that they are not substantial enough to be fatal to the infant. But, these genetic defects are thought to be the cause of the increased risk of not only autism, as observed in this study, but also schizophrenia and cancer later in life as well.
I have posted evidence