men 40 years and older were 5.75 times more likely to have a child with autism spectrum disorder

Fathering over 40
Wednesday, November 01, 2006
It's not just women who have to worry about having children over 40. New studies show that older dads
can contribute to birth disorders, also.
By Lynne Thompson
Most people think that only women have to worry about the complications age brings to delivering a
healthy baby. But a number of disorders -- everything from birth defects to schizophrenia -- have also been
associated with fathering over 40.
The latest: autism. Emily Edelman, a genetic counselor at the Cleveland Clinic, quotes a recent study that
found men 40 years and older were 5.75 times more likely to have a child with autism spectrum disorder
than men under 30. According to Edelman, the definition of advanced paternal age differs from study to
study -- "some studies say somewhere between 40 to 50, some between 45 to 50." Experts aren't sure
why the risk increases.
One theory is that as men age, there is an increase in genetic mutations in the sperm. Examples of
conditions caused by an autosomal dominant mutation -- that is, a genetic mutation on one of the
chromosomes supplied by either parent that is expressed -- associated with older fathers include
achondroplasia, one of the more common types of dwarfism, and Marfan Syndrome, a connective-tissue
disorder characterized by heart defects, weak connective tissue, extreme height and thinness, and
dislocated lenses in the eyes. "One study showed there's a 4 to 5-times increase in having a child with an
autosomal dominant condition when the dad is 45 years or older," Edelman says.
Edelman says researchers believe autism may be linked not to one specific mutation, but an accumulation
of mutations over time, while birth defects such as cleft lip and palate and extra, missing or fused fingers
may be part of a larger syndrome associated with advanced paternal age. Yet Edelman stresses that
autism and schizophrenia result from a combination of factors, including nurturing, nutrition, and
alcohol/drug use.
And Chapa points out that studies on advanced paternal age are observational in nature. He adds that
while a fourfold or fivefold increase in the chance of fathering a child with an autosomal dominant condition
may sound huge, the odds being multiplied are actually quite small.
"The incidence of these diseases in the population isn't all that high -- some of these conditions are 1 in
20,000, some are 1 in 5,000," he says. "If your risk was 1 in 5,000, then your risk is now 1 in 1,000. For a
woman of 45, the risk for having a child with a chromosome abnormality (such as Down Syndrome) is
about 1 in 20."
Birth defects such as cleft lip and palate and extra, missing or fused fingers may be part of a larger
syndrome associated with advanced paternal age.
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