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.

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"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.

There may be a promising new treatment on the horizon for advanced breast cancer patients, according to developing research.

Researchers are studying the cancer-killing drug trastuzumab rezetecan for those with ERBB2-low metastatic breast cancer, whose tumors have low levels of HER2, a protein that can help cancer cells grow.

A phase 3 clinical trial called HORIZON-Breast06 sought to determine whether the drug works better than standard chemotherapy for patients with this cancer type.

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The researchers analyzed 551 female patients across 73 hospitals in China who were randomly assigned to receive either the drug intravenously every three weeks, or the physician’s choice of chemotherapy. The study period lasted from June 2023 to August 2025.

The drug significantly delayed cancer progression compared with chemotherapy, giving patients more than a year before their cancer began growing again.

The median time without tumor growth was 16.4 months compared to 6.8 months with chemo.

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Patients who received trastuzumab rezetecan were 73% less likely to have their cancer worsen or die during the study than patients who received chemotherapy.

The drug appeared to delay cancer progression in patients with both hormone receptor-positive and hormone receptor-negative breast cancer.

The results were published in JAMA.

Tumors shrank in 75.5% of patients who received the drug, compared with 41.2% of those who received chemotherapy.

At the 12-month mark, 90.6% of trastuzumab rezetecan patients were alive, compared to 81.4% of chemo patients.

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The authors concluded that trastuzumab rezetecan provided "significant progression-free survival benefit over physician’s choice of chemotherapy in patients with ERBB2-low advanced breast cancer."

Loren Rourke, a Texas-based breast surgical oncologist and author in Texas, called the results "incredibly encouraging."

"When you're talking about women living with advanced breast cancer, those months matter," Rourke, who was not involved in the study, told Fox News Digital. "They represent more time when the cancer is being held in check and potentially more opportunities to enjoy life without the disease getting worse."

What makes these findings especially exciting, according to the oncologist, is that the treatment showed benefits across different types of breast cancer.

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"It's another important step forward, and it gives us genuine reason to be hopeful," she said. "A treatment that can keep cancer from progressing for a longer period has the potential to make an enormous difference in a patient's life."

While the drug may cause fewer serious lung problems than similar treatments, it was linked to other side effects, including anemia and other blood-related problems.

Serious side effects occurred in more than 84% of patients who received the new drug, compared with nearly 68% of those who received chemotherapy.

Rourke emphasized the importance of considering the side effects, "because more time without cancer progression doesn't automatically mean better quality of life."

"We need to better understand the side effects, particularly the significant decreases in blood counts that can lead to fatigue, anemia and increased risk of infection," she said.

The researchers acknowledged that toxicity occurred more frequently and often required dose modification, although they said these effects were "generally manageable."

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The experts agreed that more research is needed.

"As exciting as these findings are, there are still important questions we need to answer," Rourke told Fox News Digital. "We know this treatment delayed cancer progression, but we don't yet know whether it will help patients live longer. That's an important distinction."

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"It's important to celebrate meaningful progress while making sure we're asking the right questions about what comes next."