An article on Matthew Hogg’s excellent environmental resource site (www.ei-resource.org) discusses the findings of work done by Drs Bray, Gunnell and Davey Smith at the University of Bristol, which had suggested that the age of the father could be a relevant factor in assessing the risk of schizophrenia and autism in a child. The following paragraphs give the gist of the article.

What might be the mechanism that produces higher rates of disorders among children of older fathers?

The DNA in a 20-year-old male has been copied approximately 100 times but in a 50-year-old father it has been copied over 800 times. Singh and colleagues (2003) studied differences in the sperm of older and younger men. Men over age 35 have sperm with lower motility and more highly damaged DNA in the form of double-strand breaks. The older group also had fewer apoptotic cells, an important discovery. (Apoptosis is form of cell death that protects the parent organism from problems or that permits differentiation, as in resorption of a tadpole’s tail.)

A really key factor that differentiates sperm from other cells in the body is that they do not repair their DNA damage, as most other cells do. As a result, the only way to avoid passing DNA damage to a child is for the damaged cells to undergo apoptosis, a process that the study indicates declines with age. Singh is quoted in Science Blog (Sullivan, 2002) as explaining that, ‘In older men, the sperm are accumulating more damage, and those severely damaged sperm are not being eliminated’.

First published May 2007

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