Parkinsonism Co-occurrence Among Older Autistic Adults, Adults With Intellectual Disability, and a Control Sample of Adults in National Health Care Claims Data

Abstract

Emerging evidence suggests that Parkinson’s Disease (PD)-related conditions (i.e., parkinsonism) co-occur more commonly with autism than in the general population. However, prior prevalence-based studies did not account for the influence of antipsychotic usage, which is linked to secondary parkinsonism as a possible side effect, or co-occurring intellectual disability (ID). In addition, no study of incidence rates of parkinsonism among older autistic adults has been completed to date. Prevalence and incidence were examined among 56,970,786 45+ year old persons across four groups (autism only, ID only, autism + ID, and control sample) utilizing U.S.-based, individually linked Medicaid and Medicare health care claims data from 2017 to 2019. Compared with the control sample (1.57%), highly elevated prevalence of co-occurring PD-related diagnoses was found across groups (autism only: 3.83%; ID only: 4.32%; autism + ID: 4.86%). This elevation in prevalence persisted after the exclusion of individuals prescribed antipsychotic medications. Whether examining broader or narrower (excluding secondary) parkinsonism, the age-standardized incidence or risk of newly documented co-occurring parkinsonism was highest in those with autism + ID, followed by those with autism only and those with ID only, all of which far outpaced control sample findings. Overall, elevated co-occurrence of autism and parkinsonism has significant scientific, clinical, and service-system implications.