The odds that a child will develop autism could be linked to their
grandfather's age at the time they were born, a new Swedish study suggests.
The study found that men who fathered a child at the age of 50 or older were
more likely to have a grandchild with autism, suggesting that the risk might be
passed down through successive generations.
Men who had a daughter at age 50 or older were 79% more likely to have a
grandchild with autism compared to men who fathered when they were in their
early 20s, the research team reported. Men who fathered a son at age 50 or older had a 67% higher risk of having a
grandchild with the disorder compared to men who fathered a child as young
Grandfather's lifestyle choices affect you
"We tend to think in terms of the here and now when we talk about the effect
of the environment on our genome," said study co-author Dr Avi Reichenberg, who
worked on the study while at King's College London's Institute of Psychiatry, in
England. "For the first time in psychiatry, we show that your father's and
grandfather's lifestyle choices can affect you."
"This doesn't mean that you shouldn't have children if your father was old
when he had you, because while the risk is increased, it is still small," added
Reichenberg, who is now an autism researcher at the Icahn School of Medicine at
Mount Sinai, in New York City.
"However, the findings are important in understanding the complex way in
which autism develops."
Although the study found a correlation between advanced age in grandfathers
and the odds for autism in children, it is only an observational trial, so it
cannot prove cause and effect. And another expert also stressed that the
absolute risk to any one family remains small.
"Although there was a statistically significant increase in the incidence of
autism in families with older grandparents, it must be remembered that autism
was still extremely infrequent even in families with the oldest grandparents,"
said Dr Andrew Adesman, chief of developmental and behavioural paediatrics at
Steven & Alexandra Cohen Children's Medical Center of New York, in New Hyde
"Thus, older parents and grandparents should not be unduly worried."
The new research was published on the same day that the US Centers for
Disease Control and Prevention announced that one in every 50 US school children
now has an autism spectrum disorder - up from the 2007 estimate of 1 in 88.
The CDC says improved detection and diagnosis are probably responsible for
most of that increase.
What the new study found
In the new study, researchers looked at data from Sweden's national
registries and compared about 6 000 people with autism to about 31 000 people
without the condition. They looked at the age of each person's maternal and
paternal grandfather at the time of the individual's birth.
The link between autism and a grandfather's age was significant, the team
said, and pointed to the genetic underpinnings of the condition. They noted that
previous studies have found a link between older fathers and rising odds for
autism in their children, such that men who have a child when age 50 or older
have a double the risk of having a child with the disorder.
Mutations lying within sperm cells might be the culprit, the researchers
said. Sperm cells undergo division throughout the life span, and with each new
division errors in the genome can occur. Some of these mutations might remain
"silent" in a man's child but then accumulate or re-emerge to cause problems in
"These findings add further support to the belief that subtle genetic
abnormalities - defects that were previously undetectable - are likely
responsible for some cases of autism," Adesman said.
This type of research might lead to tests that could pinpoint a child's odds
for an autism spectrum disorder, he added. "Newer molecular genetic laboratory
tests will increasingly allow scientists and doctors to find atypical parts of
chromosomes that put a child at increased risk for an autism spectrum disorder,"
Another expert said the new study could raise as many questions as it
Although the researchers offer theories as to how a man's age might affect
the risk for autism in his descendants, "more research is needed to better
understand how this occurs," said Alycia Halladay, senior director for
environmental and clinical sciences at the advocacy group Autism Speaks. "For
example, it could be through modifications of DNA, or it could result from
environmental factors modifying how DNA is expressed," she said.
"This study is important because it utilises rich data sets with health
record information," Halladay added. "This approach can open the door for future
work on genetic and environmental factors associated with [autism spectrum
Find out more about autism spectrum disorders at the American Psychiatric