Common developmental condition linked to higher risk of Parkinson's-related disorders

Older adults diagnosed with autism face a significantly higher risk of developing Parkinson’s disease-related movement disorders compared to the general population, according to a large new study published in the journal Autism.

Researchers analyzed Medicare and Medicaid claims data covering nearly 57 million Americans aged 45 and older between 2017 and 2019.

Individuals on the spectrum, as well as those with intellectual disabilities, were diagnosed with parkinsonism at much higher rates than those without autism.

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Parkinsonism refers to a range of neurological conditions characterized by certain movement symptoms, including tremors, muscle rigidity, balance difficulties and slowed voluntary movement, according to the Parkinson’s Foundation.

While earlier research suggested an overlap between autism and motor decline later in life, it was unclear whether those problems stemmed from the condition or from antipsychotic medications, which are widely known to trigger Parkinson’s-like symptoms as a secondary side effect.

To determine whether medications explained the link, researchers excluded people who took antipsychotics from the analysis. They still found higher rates of Parkinson’s-related diagnoses in neurodivergent populations.

In the general population control group, the prevalence of parkinsonism was roughly 1.57%. The prevalence rose to 3.83% among adults with autism alone, 4.32% for those with an intellectual disability alone, and 4.86% among individuals diagnosed with both autism and an intellectual disability.

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"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," Greg Wallace, lead author and a professor in the Department of Speech, Language and Hearing Sciences at The George Washington University in Washington, D.C., said in a press release.

The study represents the first time scientists have tracked the incidence rate, or the risk of newly emerging cases over time, among older autistic individuals.

"It is therefore important for clinicians to establish clear baselines of motor skills and challenges during adulthood that can be tracked over time," Wallace added.

Dr. Lee Murray, a neurologist based in Jackson, Tennessee, said this study clarifies previous research that suggested patients with autism are at a higher risk of having Parkinson's.

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"This study takes into account the use of antipsychotic medications that can cause a Parkinson's look (resting tremor, stiffness, shuffled gait, stooped posture, softened voice), which is a different pathology than stereotypical or idiopathic Parkinson's disease," Murray, who was not involved in the study, told Fox News Digital.

"This study showed patients with autism that was associated with intellectual disability seem to have the greatest association with concomitant Parkinson's."

The neurologist cautioned that autism encompasses a wide range of symptoms and severity, so the findings don't mean that people with milder cases face a significantly higher risk of Parkinson’s disease.

"It certainly is an interesting correlation, although it does not imply that someone with autism is certain to develop Parkinson's," Murray added.

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"From a clinical perspective, it's helpful to review medications with the autistic patient's physicians and, if possible, try to avoid medications that may cause a Parkinson's appearance."

Despite the scope of the data, the authors noted several key limitations of using insurance records.

The investigation relied on billing and diagnostic codes submitted through Medicare and Medicaid, which can contain errors or reflect differences in how clinics and medical providers diagnose conditions.

The reliance on claims data also means researchers could not assess the severity of individual motor symptoms or examine the role of lifestyle factors, genetics and family history, they noted.

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Additionally, the data only captured adults who were enrolled in public insurance programs, potentially leaving out older individuals who rely strictly on private health insurance.

Because people on the autism spectrum may already struggle with coordination, repetitive behaviors or executive functioning challenges, experts say early indicators of Parkinson’s disease can be missed or mistaken, potentially delaying essential care.

"Patients with autism can have atypical movements that can be misdiagnosed as Parkinson's if the examiner is not accustomed to diagnosing it," Murray confirmed.

The researchers emphasized the need for physicians, long-term care facilities and family caregivers to closely monitor older autistic patients for motor decline so interventions can begin as early as possible.