Study links older parents to rise in autism risk

Study links older parents to rise in autism risk
BY JANET ZIMMERMAN | The Press-Enterprise
November 4, 2008
The firstborn children of older parents are three times more likely to have autism than their siblings or those born to younger parents, according to a new federally funded study.

This is the largest study to look at the issue of parental age and its role in the developmental disability, said the author, Maureen Durkin, an epidemiologist at the University of Wisconsin School of Medicine and Public Health.

The study, funded by the U.S. Centers for Disease Control and Prevention, was published in last month's American Journal of Epidemiology. The ages for increased risk were in women over 35 and men over 40, Durkin found.

But she cautioned that many other factors could play a role in autism, including environmental causes, so prospective parents should not decide against having children because of the findings.



"Even though we find this association statistically significant, I don't think it's a strong enough relationship to affect family planning decisions," Durkin said. "Even with this strong increase in risk, the vast majority of children born to older parents - more than 95 percent of these births - are not going to have autism." Durkin's research looked at 253,347 births from 10 states that participate in the CDC's Autism and Developmental Disabilities Monitoring Network. All births were in 1994 and included 1,251 children with autism.

The results echoed a smaller Kaiser Permanente study of California children that was published last year. That research traced an autism link when both parents were over 35.

Autism and related disorders affect 1 in 150 U.S. children. It is characterized by impaired communication and social interaction and repetitive patterns of behavior such as hand flapping and spinning.

It is the fastest-growing developmental disability in the United States, and its prevalence worldwide has more than doubled in the past 20 years.

While Durkin's research doesn't fully answer questions about autism, it does provide clues for further research into the causes, she said, among them, factors associated with older parents.

Those factors that bear further investigation are: spontaneous mutations that occur in sperm as men age; fertility treatments that involve hormonal treatments and manipulations of genes during conception; and neurotoxins built up in the tissues of older, breast-feeding mothers, Durkin said.

Each 10-year increase in maternal age was associated with a 20 percent increase in autism risk and a decade added to the father's age kicked up the risk to 30 percent, according to the study.

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