Autism Tied to Fourfold Higher Rate of Parkinsonism

Middle-aged and older adults with autism spectrum disorder have more than twice the rate of parkinsonism as their peers without the disorder, a large US study showed.This association persisted even after investigators accounted for antipsychotics and other medications that can cause Parkinson-like symptoms.The higher rates of newly diagnosed parkinsonism in this population suggest the findings cannot be explained solely by lifelong motor challenges, lead investigator Gregory L. Wallace, PhD, from The George Washington University in Washington, said in a press release.“It is therefore important for clinicians to establish clear baselines of motor skills and challenges during adulthood that can be tracked over time,” he added.The findings were published online on October 24 in Autism.Four- to Fivefold Increased RiskPrevious research suggest that adults with autism may be more likely to develop parkinsonism. However, past studies have generally been relatively small or have not adequately accounted for intellectual disability or the use of antipsychotics.To address these gaps, Wallace and colleagues analyzed linked Medicaid and Medicare claims data from 2017 to 2019, covering nearly 57 million adults aged 45 years or older across all 50 states and Washington.The study population included 39,507 adults with autism alone, 69,423 with autism and intellectual disability, 544,842 with intellectual disability alone, and more than 56 million control participants without either diagnosis.The prevalence of parkinsonism was significantly higher in all three groups than in control group. It was 3.8% with autism alone, 4.3% with intellectual disability alone, 4.9% with both, and 1.6% in control participants.Compared with control participants, the unadjusted prevalence of parkinsonism was 2.44 times higher in adults with autism alone, 2.76 times higher in those with intellectual disability alone, and 3.10 times higher in those with both conditions (P < .05 for all).After excluding individuals prescribed medications associated with drug-induced parkinsonism and adjusting for demographic and other factors, the prevalence of parkinsonism remained 67% higher in adults with autism alone (adjusted prevalence ratio [PR], 1.67), 94% higher in those with intellectual disability alone (PR, 1.94), and 85% higher in those with both conditions (PR, 1.85) compared with control participants.The researchers also examined the rate of newly diagnosed parkinsonism. Age-standardized incidence rates among adults aged 45 years or older were 1341 cases per 100,000 person-years among those with both autism and intellectual disability, 1017 among those with intellectual disability alone, and 977 among those with autism alone compared with 234 among control participants.Results showed the rate of newly diagnosed parkinsonism was approximately 5.7 times greater among adults with both autism and intellectual disability and 4.2 times higher among those with autism alone compared to control participants.The pattern persisted in sensitivity analyses restricted to a narrower definition of parkinsonism that excluded secondary parkinsonism diagnoses, as well as in analyses of Medicaid and Medicare recipients separately.Questions RemainThe researchers cautioned that longstanding motor difficulties associated with autism may mask newly emerging parkinsonism.“Because these earlier emerging motor symptoms could diagnostically overshadow parkinsonism symptoms, disentangling them can be challenging,” they wrote.Establishing when symptoms first appeared and documenting changes over time may help clinicians distinguish longstanding motor differences from new movement abnormalities that warrant further evaluation, they added.The researchers also noted that the association between autism and parkinsonism remains poorly understood. The findings do not establish whether autism itself increases susceptibility to Parkinson’s disease or whether other shared biological, clinical, or environmental factors contribute to the association.Study limitations include the reliance on administrative claims rather than independent neurologic assessments. The relatively short observation period limited assessment of longer-term disease development, and the findings may not generalize to all adults with autism.The researchers called for further research to clarify the mechanisms underlying the association between autism and parkinsonism and emphasized the need for better coordination of care for aging adults with autism.The study was supported by grants from the National Institutes of Health and the Health Resources and Services Administration. The authors declared no conflicts of interest.