Dr Karin Hammarberg ... said that while most children are born healthy, large studies of parental age were starting to show higher rates of birth defects and autism in children born to men over 40.
A recent review of paternal age published in the Asian Journal of Andrology said an American study of 132,000 men found children of those over 45 were nearly six times more likely to have an autism spectrum disorder compared to children born to men under 30.
The review also pointed to a Dutch study of 60,000 births which found children born to men over 40 were three times more likely to have autism and a US study of 5 million births which showed men over 50 had a 15 per cent higher chance of having a baby with birth defects including congenital heart disease and cleft palates.
However, my first thought was that the age of the father must be highly correlated with the age of the mother. Thus, an alternative explanation is that the higher prevalence of birth defects for older fathers is due to the fact that older fathers typically have babies with older mothers. Of course, the same argument could be made for the reported higher prevalence of birth defects in older mothers (i.e., they're having babies with older fathers).
- To what extent is paternal age associated with prevalence of birth defects after controlling for maternal age?
- To what extent is any association between paternal age and prevalence of birth defects causal? (maternal age is the main covariate that I could think of, but there might be other important confounding variables)