Middle-aged and older adults with autism are more likely to have co-occurring parkinsonism than adults without autism or intellectual disability, according to a new study led by George Washington University researchers in the Department of Speech, Language and Hearing Sciences.
The study also found that adults with both autism and intellectual disabilities had the highest rates of parkinsonism among the groups examined.
Parkinsonism is a general clinical syndrome that covers any condition that causes the motor symptoms associated with Parkinson’s Disease.
The research team, including Greg Wallace, a speech professor at GW’s Columbian College of Arts and Sciences and lead author on the study, analyzed healthcare data from nearly 57 million people ages 45 and older to examine the prevalence and incidence of parkinsonism among adults with autism, intellectual disabilities or both.
The researchers found that 3.83% of adults with autism, 4.32% of adults with intellectual disabilities and 4.86% of adults with both autism and intellectual disabilities had co-occurring parkinsonism, compared with 1.57% of adults in the control group.
The elevated rates remained even after researchers excluded people prescribed medications linked to drug-induced parkinsonism, including antipsychotic medications. Although medication use appeared to contribute to the higher rates, adults with autism and/or intellectual disability continued to have elevated rates compared with the control group.
“Utilizing the largest sources of healthcare for middle- and older-aged Americans, this study demonstrates an increased propensity for autistic adults to experience parkinsonism, joining a growing body of research,” Wallace said.
“A critically important new contribution of this study is increased incidence rates (or newly identified/emerging cases) of parkinsonism for autistic people in middle and older adulthood, which suggests that these cases aren’t simply a byproduct of lifelong motor challenges,” Wallace noted. The findings, he said, stress the importance of clinicians establishing clear baselines of motor skills and challenges during adulthood that can be tracked over time.
The researchers also examined newly documented cases of parkinsonism among middle-aged and older adults. For adults ages 45 and older, the age-standardized rate was highest among adults with both autism and intellectual disability, at 1,341 cases per 100,000 person-years, followed by adults with intellectual disability alone, at 1,017, and adults with autism alone, at 977. The rate was 234 in the control group. Analyses using a narrower definition that excluded secondary parkinsonism showed the same overall pattern.
The study, titled “Parkinsonism Co-Occurrence Among Older Autistic Adults, Adults with Intellectual Disability, and a Control Sample of Adults in National Healthcare Claims Data,” is based on individually linked Medicaid and Medicare claims data from 2017 to 2019, covering all 50 states and Washington, D.C. Researchers examined diagnoses, healthcare use, prescriptions and demographic information among adults ages 45 and older who were continuously enrolled for at least 12 months.
The findings could have implications for how healthcare providers monitor and treat autistic adults and adults with intellectual disabilities as they age. The researchers note that distinguishing newly emerging motor symptoms from motor differences that may have existed earlier in life can be challenging, making an individual’s history of motor symptoms particularly important.
The researchers say more work is needed to understand why parkinsonism occurs at higher rates among these populations, including research examining the age at which parkinsonism begins and factors that may predict its development. Because the study relied on healthcare claims, the findings reflect documented diagnoses rather than independent clinical evaluations. The results also point to potential implications for Medicaid and Medicare systems, particularly in coordinating care for people with complex healthcare needs.
The co-researchers on the study, which appeared in the journal “Autism,” are from the University of North Carolina at Chapel Hill, Drexel University and the University of Pennsylvania.