Autism Linked to Higher Parkinson's Risk, Study Finds

Adults diagnosed with autism are at a significantly higher risk of developing Parkinson’s disease-related movement disorders compared to the general population, according to a large study published in the journal Autism. The research analyzed Medicare and Medicaid claims data for nearly 57 million Americans aged 45 and older between 2017 and 2019.

Individuals on the autism spectrum, as well as those with intellectual disabilities, were diagnosed with Parkinsonism at substantially higher rates than those without these conditions. Parkinsonism encompasses a group of neurological conditions characterized by symptoms such as tremors, muscle rigidity, balance issues, and slowed voluntary movement.

Previous research had suggested a connection between autism and motor decline in later life, but it was unclear if these issues were a direct result of the condition or a side effect of antipsychotic medications, which are known to cause Parkinson's-like symptoms. To address this, the researchers specifically excluded individuals taking antipsychotics from their analysis and still observed elevated rates of Parkinson’s-related diagnoses in neurodivergent populations.

The study found that the prevalence of Parkinsonism in the general population control group was approximately 1.57%. This rate increased to 3.83% for adults with autism alone, 4.32% for those with an intellectual disability alone, and 4.86% for individuals diagnosed with both autism and an intellectual disability.

"A critically important new contribution of this study is increased incidence rates of parkinsonism for autistic people in middle and older adulthood, which suggests that these cases aren’t simply a byproduct of lifelong motor challenges," stated Greg Wallace, lead author and a professor at The George Washington University. This study marks the first time scientists have tracked the incidence rate of newly emerging cases of parkinsonism over time among older autistic individuals.

Dr. Lee Murray, a neurologist not involved in the study, commented that this research clarifies previous findings by differentiating Parkinsonism associated with autism from drug-induced symptoms. "This study showed patients with autism that was associated with intellectual disability seem to have the greatest association with concomitant Parkinson’s," Murray noted. He also cautioned that autism is a spectrum with varying severity, and these findings do not imply a certain diagnosis for individuals with milder cases.

The study's authors acknowledged limitations inherent in using insurance claims data, such as potential coding errors and variations in diagnostic practices. The reliance on claims also meant researchers could not assess the severity of individual motor symptoms or consider lifestyle factors, genetics, or family history. Furthermore, the data primarily covered individuals enrolled in public insurance programs, potentially excluding those with only private health insurance.

Experts emphasize that the early signs of Parkinson's disease can be subtle and may be overlooked or misattributed to existing challenges in coordination, repetitive behaviors, or executive functioning common in autism, potentially delaying critical interventions. The researchers recommended that clinicians, long-term care facilities, and caregivers closely monitor older autistic patients for signs of motor decline to facilitate timely intervention.