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Researchers say the age of a child’s grandparents may also play a role in the chance of having autism spectrum disorder. Getty Images
  • Researchers say the chance of having autism spectrum disorder appears to increase with the age of the parents when a child is born.
  • They add that the age of the child’s grandparents may also be a factor.
  • Experts say more study is needed and note that environmental factors also need to be considered.

Could the age of parents, and even grandparents, increase the chance of having autism spectrum disorder (ASD)?

That’s what the latest research is examining as part of the long-standing debate over what’s causing an increasing number of ASD diagnoses in children.

The Centers for Disease Control and Prevention (CDC) estimates 1 in 54 children born in the United States have been identified as having ASD.

It occurs in all racial and socioeconomic groups, and it’s four times more common among boys than girls.

The CDC says a broader definition of ASD and better diagnostic efforts could be factors in increased diagnoses, but scientists can’t rule out a true spike in numbers.

After decades of research, little is known about the causes of ASD.

Multiple studies have pointed to older parents as a factor, with some even singling out older fathers.

Now, a new study looks at not just the age of the parents when it comes to increased chances of ASD, but also the age of the grandparents when the parents were born.

The study, titled Association of Grandparental and Parental Age at Childbirth with Autism Spectrum Disorder in Children, was published in JAMA Network Open last week.

“What is more interesting in this paper is that we evaluated a new hypothesis focusing on potential ‘transgenerational risk’ for [autism spectrum disorder],” said Zeyan Liew, PhD, MPH, an assistant professor of epidemiology at the Yale University School of Public Health in Connecticut and a corresponding author of the study.

“Our findings of grandparental age at the time of the birth of parents and future risk of [autism spectrum disorder] in the grandchild is novel,” Liew told Healthline. “It suggests that possible transmission of [autism] risk across generations should also be considered in future etiological research.”

The team of researchers studied data from Danish national health registries that included three generations and nearly 1.5 million children.

They found that the chance of having ASD for children born to parents who are in their 30s is up to 10 percent higher than parents who are 25 to 29 years old.

The researchers also reported that the chance is 50 percent higher when the parents are in their 40s or 50s.

“We observed that children with young maternal grandparents and children with young and old paternal grandparents had higher [autism] risk compared with children of grandparents who were 25 to 29 years old at the time of the birth of the parents,” Liew said.

He says these findings, however, are unique and “require further replications.”

“The finding of increased risk in younger grandparents is novel,” said Thomas Frazier, PhD, a professor of psychology at John Carroll University in Ohio and the former chief science and program officer for Autism Speaks.

“It could mean that young grandparents convey some risk to their children that magnify, or at least complement, increased risk in the parent,” Frazier told Healthline.

“For example, if young grandparents also have less money, and this results in poorer nutrition, that could impact the biology of the parent. These biological impacts might then be magnified in older parents,” he added.

Frazier says the study suggests there may be some environmental factors that affect the child. But he says the results need to be repeated and show whether the grandparent effect remains after controlling for the advanced parental age.

“For research, it suggests we should try to understand the factors, genetic and possibly epigenetic, that get transmitted from parent to child, and how this seems to result in greater problems for the child in older parents,” he explained. “Are there ways we can reduce these impacts? Supplementation? Exercise? Other parent health factors?”

Bottom line? “We need to study this more,” Frazier said.

Jenn Lynn is the mother of a son with ASD. She’s an ASD advocate and the executive director of Upcounty Community Resources, a nonprofit serving those with disabilities.

Healthline asked Lynn for her reaction to the study.

“I believe all knowledge is power and always try to learn as much as I can about things impacting our community,” she said. “However, I feel rather helpless after seeing these results. As a parent, armed with this information, I could plan to have children earlier, but there is absolutely nothing to be done about what age my grandparents were when my mother or father was born.”

Lynn says she hopes when looking back over generations for clues, more research will focus on the role environmental factors, such as pesticides, preservatives, and processed foods, may play.

“While some people agree that finding a cause for autism is the most important thing to focus on, I tend to deal with my reality at this moment,” Lynn said.

“Admittedly, parenting a child with autism is more challenging,” she added. “There is much to be gained having an [autistic] child or relative in your family.”

The researchers said with the increasing trend worldwide of postponing parenthood, there’s considerable interest in the possible association of ASD chance with grandparents age.

“There is a multifactorial nature for [autism spectrum disorder] etiology, including a range of genetics and environmental risk factors that might contribute,” Liew said.

“It is also important to find out whether there are any other modifiable risk factors that are correlated with age of delivery that we could prevent or intervene that could help mitigate the risk for ASD in the offspring of very young or older parents,” he added.

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