Epidemiology of Alzheimer Disease and Related Dementia Among Medicare and Medicaid Enrolled Autistic Adults, 2011-2019

Alzheimer's disease and related dementias (ADRD) are burdensome and lethal conditions that have been hypothesized to be related to autism through shared genetic etiologies and environmental risk factors. Our objective was to use longitudinal Medicaid and Medicare data to describe the epidemiology of ADRD in publicly insured autistic adults. We used all claims and encounters from 2011 to 2019 to identify autism and ADRD. We calculated prevalence, incidence, age at onset, and created survival curves. There were 90,229 autistic adults >= 30 years of age and enrolled for at least 1 year in Medicaid and/or Medicare and 267 ADRD cases. Prevalence of ADRD was 2.09% (95% CI: 1.99%, 2.20%) in 2011 and 8.11% (95% CI: 7.92%, 8.30%) in 2019. Mean age at ADRD onset was 59.3 years (SD: 14.2). Mean age among men was 58.3 years (SD: 13.8) and 61.0 years among females. Incidence of ADRD was higher in autistic adults with intellectual disability with no difference by sex. ADRD is a prevalent condition in middle- and older-aged adults identified with autism in the Medicaid and Medicare system. Understanding the diagnostic process and phenotype of ADRD will be important to improve identification and treatment.