ASD: Why comorbidities may increase mortality risk

Premature mortality is already associated with the presence of autism spectrum disorder (ASD), but a recent study from Denmark suggests that mortality rates could be even higher in patients with ASD and another comorbidity.

Autism spectrum disorder is characterized by neurodevelopmental deficits such as impaired social communication and repetitive behaviors. With prevalence increasing over the last decade from 1% to 2%, researchers say it is important now to understand more about the long-term effects of ASD.

Related: What happens after losing an ASD diagnosis?

Previous studies have reported a higher mortality rate in persons with ASD, particularly when other comorbidities like epilepsy or intellectual disability are present. Prior research, according to the new study, has indicated that medications, and poor lifestyle and behavior choices may contribute to mortality rates for individuals with ASD.

Healthcare providers and families must try to gain insight into the underlying pathogenesis that may lead to premature mortality, says Diana Schendel, Professor MSO at Aarhus University in Aarhus, Denmark and lead author of the study.

The study involved nearly 2 million Danish children-more than 20,000 with ASD. Researchers hoped to determine the effects of ASD and other mental, behavioral, and neurologic conditions on the mortality risk of the individuals in the cohort. They found that individuals with ASD and no other comorbidities had a 1.7- to 2.0-fold increased risk of mortality overall.

However, for those with other comorbidities, mortality risks are greater.

“Having both ASD and these other comorbid conditions increased the risk of death (2.6- to 7.6-fold) compared with persons without ASD and without these other comorbid conditions,” according to the report.

Autism spectrum disorder was found to most likely in those who were male, born prematurely with birth weights on the high or low end of the spectrum, and who had older parents or parents with a history of psychiatric disorders. According to the report, 1% of the children studied overall had ASD, and 78% of persons with ASD were male.

Although ASD and premature death aren’t necessarily common-affecting just 1% of the cohort studied-many of those in that group had comorbidities and a high risk of early death.

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“Although the risk of premature death in ASD is 2-fold higher than in persons without ASD, mortality is fortunately quite rare in adolescent and young adults, affecting only 0.3% of diagnosed persons with ASD in our cohort,” says Schendel. “The majority of deaths in ASD were in persons with ASD and comorbid mental, behavioral, or neurologic disorders and mortality risk was significantly elevated in persons with ASD and these other morbidities, compared to persons without any of these disorders.”

Schendel says 23% of the ASD deaths were the result of suicide, corresponding with a 4.6-fold increased risk for mortality from suicide in persons with ASD.

There were more deaths associated with ASD in males, but women with ASD had a higher relative risk of death, Schendel says.

More: Why kids need ongoing care after they lose ASD diagnosis

Roughly a quarter-26%-of deaths were due to accidents, but Schendel says the risk of death by accident in individuals with ASD were not significantly elevated compared to persons without ASD.

Sixty-eight individuals with ASD in the study died at age 19 years-about 5.5 years after their diagnosis. Another 16 individuals with childhood autism died at about 18.5 years of age-again, roughly 5 years after their diagnosis.

Researchers found a 4.1-fold risk of death from neurologic causes among persons with ASD, a 4.6-fold risk of death from intentional harm, and a 40% increased risk of death caused by accidents in individuals with ASD. Overall, individuals with ASD and no other comorbidities have a 2-fold increased risk for death.

Of the cohort with ASD and at least 1 comorbidity at the time of death, about 32% had a mental, behavioral, or neurologic condition. Two-thirds of those that died of external causes had a mental or behavioral comorbidity, and half of those that died from natural causes had both mental/behavioral and neurologic conditions.

Overall, Schendel says 22.8% of persons with ASD died of self-inflicted injuries; 26.3% died in accidents-although this statistic is not significantly greater than in individuals without ASD.

“The majority of individuals with ASD whose death was due to either intentional self-harm or an accident had mental/behavioral comorbid conditions,” according to the researchers.

Many of the possible reasons for increased mortality in ASD and the comorbid conditions-including poor diet and exercise habits, sedentary lifestyle, weight gain related to medications, negative social conditions-can be modified in some way, according to the report.

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“Poor medical monitoring of young adults, which could lead to undetected health problems, could be a contributing factor, possibly exacerbated in ASD by poor social communication skills, resistance to new experiences, and altered perception rendering them less likely to seek healthcare,” according to the report. “Because many of these mortality risk factors are shared across the disorders, these common factors could underlie the apparent shared risk for mortality between other psychiatric and neurologic disorders and ASD.”

There may be a connection in the underlying mortality risks of ASD and other neurologic, mental, and behavioral disorders, according to the researchers, although this study did not reveal what those connections may be.

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“It is important for care providers, persons with ASD and their families to recognize the importance of neurologic, mental, and behavioral comorbidity in the risk of mortality in ASD and consider preventive measures, including the risk for suicide,” Schendel says.

According to the National Autism Association, roughly half of children with ASD attempt to escape to safe environments and wander off, and 91% of accidental drownings in children with ASD were the result of elopement. Despite the fact that many parents of children with ASD share fears of elopement or close calls with injury as a result of their children wandering off, half of parents of children with ASD says they were never counseled about this risk by a healthcare provider. In fact, only 19% say they were warned by mental health professionals and 14% were warned by primary care physicians or pediatricians about the risk of elopement in children with ASD.

A Swedish study from 2010 also makes the connection between early mortality in individuals with ASD, revealing that individuals with ASD had a mortality rate 5.6 times greater than what was expected. Researchers in that study attributed higher rates of mortality to comorbid medical conditions such as epilepsy and accidental death to the increased prevalence of premature mortality.

The American Academy of Pediatrics has developed a toolkit for promoting safety in children with ASD for clinicians, and offers guidance on early intervention, treatment of comorbidities, and methods for supporting families. The National Autism Association also offers guidance on managing elopement, including creating a family emergency plan and making sure children carry identification with them at all times.