STOCKHOLM, Sweden, March 21 (UPI) -- People with autism spectrum disorder live about 18 fewer years than average, and the leading cause of early death among adults on the spectrum is suicide, according to a recent study in Sweden.
Researchers suspect the shorter lifespan is a combination of health and social factors, but said whether ASD itself is the cause of early death is unknown.
With or without the intellectual disabilities that often accompany ASD, researchers said bullying and questions of self-worth often start early in life for people on the spectrum. Previous research has shown between 30 percent and 50 percent.
"This new research confirms the true scale of the hidden mortality crisis in autism," Jon Spiers, chief executive of Autistica, which published a report on the Swedish study, said in a press release. "The inequality in outcomes for autistic people shown in this data is shameful. We cannot accept a situation where many autistic people will never see their 40th birthday."
For the study, published in the British Journal of Psychology, researchers compared medical data on 27,122 people with an ASD diagnosis and 2,672,185 without a disorder in Sweden collected as part of the National Patient Register and the Cause of Death Register by the country's national health service.
People with ASD had a 2.56-fold increased risk of death compared to those without a diagnosis, in men the odds were worse than women and both low- and high-functioning people were at greater risk, though lower function increased the risk of death.
Compared to an average age of death of 70.20 years for those without ASD, the average age of death among people with ASD and no intellectual disability was 53.87 years, while for people with ASD and intellectual disability it was 39.5 years.
In the study, adults with ASD and no learning disability were nine times more likely than the general population to commit suicide. Part of this, researchers found, is that 70 percent of ASD patients have a mental health disorder, such as anxiety or depression, and as many as 40 percent have two disorders.
The second leading cause of death among ASD patients is epilepsy, which between 20 percent and 40 percent have.
"Across every major cause of death, mortality risk is increased in autism, but early deaths due to epilepsy and suicide are particularly, and unacceptably, high," researchers at Autistica write in their report. "We cannot and should not accept that many people on the autism spectrum will die 30 years before the typical population."