While the incidence of autism spectrum disorder has increased in recent years, what’s behind it remains relatively mysterious and even controversial. But a major study could shed new light on some of the maternal health factors that may increase children’s risk of developing the condition.
Autism is a neurodevelopmental disorder marked by difficulties with communication and social interaction as well as repetitive or obsessive behaviors. The range and severity of symptoms can vary widely.
The study, which was released Friday and appears in the February issue of the journal Pediatrics, followed almost 3,000 children who visited the Boston Medical Center between 1998 and 2014. It used electronic health records to track whether these children were diagnosed with autism, along with factors like the mother’s pre-pregnancy weight and whether she had been diagnosed with diabetes before or during her pregnancy.
Though previous research has looked at the roles of maternal obesity and diabetes on autism risk, this study is the first to examine both the independent and combined effects of the two.
The researchers found that of the nearly 3,000 children in the study, about 100 were identified as on the autism spectrum.
They also concluded that obese women who contracted diabetes while pregnant — a condition known as gestational diabetes — were about three times as likely to have children with autism. Women who were obese and had diabetes before pregnancy were almost four times as likely. In addition, children with autism were more often boys, more often born before 32 weeks and more often had very low birth weight. Beyond being obese and diabetic, their mothers were also more likely to be older.
Having just one of the conditions, however, posed only a slight risk increase.
Overall, though, the risk was “substantially higher” when women had both, according to the study.
It “calls attention to the idea that maternal prenatal health and maybe even pre-pregnancy health may be important factors for autism — and may be important opportunities for protection from autism,” said study co-author Daniele Fallin, who chairs the department of mental health and directs the Wendy Klag Center for Autism and Developmental Disabilities at the Johns Hopkins Bloomberg School of Public Health.
The findings are important because, if doctors have a better sense of autism’s causes, they can try to reverse the current trend lines and stem its growth, Fallin said.
In 2010, the most recent year for which there’s data, about 1 in 68 children were estimated to have autism. That’s a contrast to 10 years prior, in 2000, when 1 out of 150 children were believed to have it. Experts say part of the growth likely is because people are simply getting better at recognizing and diagnosing the disease. But, according to the Centers for Disease Control and Prevention, the disorder is also probably occurring more often than it used to.
“The cost per family per year of having a child on the spectrum is enormous — therefore societal costs are enormous,” Fallin said. “If you can do anything to stem the tide of rising prevalence, or even drop the prevalence, then absolutely, you should. Not only individual families benefit, but society benefits.”
A different study published last year in the Journal of Autism and Development Disorders estimated that taking care of people with autism cost the country about $268 billion in 2015 — a figure that accounts for medical expenses, other kinds of caregiving and the decreased productivity both from people who care for autistic relatives and for adults on the spectrum.
If the increase in prevalence continues at its current rate, this expense will grow markedly, that study noted.
From a cost standpoint, then, the new research underscores the importance of preventing obesity and diabetes, said Paul Leigh, a professor of public health sciences at the University of California, Davis, who authored the autism cost study. Because of the autism tie, “there are more reasons to be worried about [obesity and diabetes], and to direct resources to removing this problem.”
The Pediatrics paper is significant, both for its findings and for its comprehensiveness in examining medical records from a large sample, said Alycia Halladay, chief science officer at the Autism Science Foundation. It suggests that if policymakers and insurers put more money into treating diabetes and obesity, the public as a whole could benefit, especially if that fuels a decline in autism cases.
“Instead of demonizing mothers with diabetes, we need to be using this as an opportunity to help them mitigate their risks as much as possible,” she said.
But, she added, it’s important to recognize that the study examines two of many factors that could put a child at risk for autism. Giving birth later in life, getting a viral infection while pregnant or being exposed to air pollution or certain medications can also be factors — so preventing autism will require a multi-pronged strategy.
“I don’t think you can look at any one of them and say, ‘Oh, it’s because of this, it’s because of air pollution, it’s because women are waiting to have babies,’” she said. “It’s a combination.”