Study links parental age to increased risk of autism

Study links parental age to increased risk of autism



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10:00 PM PST on Sunday, November 2, 2008

By JANET ZIMMERMAN
The Press-Enterprise

The first-born 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 age limits where Durkin found the increased risk were in women over 35 and men over 40.

But Durkin cautioned that many other factors could play a role in autism, including environmental causes, and would-be parents should not put off 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 in a telephone interview. "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, which affects 1 in 150 American children, 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, Durkin said.

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, breastfeeding 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.

The mean maternal age in the United States has increased steadily -- by 3.8 years -- between 1970 and 2004, especially for first-time mothers. Durkin questioned how much of a role advanced parental age and fewer children per family plays in the staggering growth in autism in recent decades.

"It might be playing some role, in particular if the families affected are better established and educated. They may be pushing more for better diagnoses and services, and may be more effective at that than younger and less well-educated parents," she said.

Beth Burt, president of the Inland Empire Autism Society, said she is pleased that money is being spent on studies into the cause of autism.

But she worried that Durkin's findings will prompt people to blame parents.

"I don't want society to go 'It's all the parents who are waiting to have kids that are causing the epidemic.' We have plenty of parents in their 20s where that isn't the case," she said.

Burt has a 15-year-old son with high-functioning autism. She was 28 when she gave birth.

Burt said she believes there are different types of autism and different triggers that require individualized and varied treatments. In addition to research studies, the government also needs to spend money on services for families, including employment and residential options.

"I'm glad they're funding studies, but I want to see something to help the families that are here now battling this," she said.

Reach Janet Zimmerman at 951-368-9586 or jzimmerman@PE.com.