Brief Report: Alzheimer's Disease and Related Dementia in People With Intellectually Disability in the United States

People with intellectual disability (ID) are living longer lives than in generations past, and experience aging-related health issues, like Alzheimer's disease and related dementia (ADRD). Our objective was to document prevalence and age of diagnosis of ADRD in the population with ID (excluding Down syndrome) ≥30 years old in the United States from 2011 to 2022 enrolled in Medicaid and/or Medicare. We measured ADRD and ID using International Classification of Disease-9/10 claims algorithms and examined demographics and trends in ADRD. We examined age at incident ADRD diagnosis. Among 1,046,621 adults with ID ≥30 years old enrolled in Medicaid and/or Medicare between 2011 and 2022, 184,206 (17.6%) had claims for ADRD, corresponding to an 11-year prevalence of one case per 5.7 people. Yearly prevalence was lowest in 2011 (11.3%) and highest in 2019 (16.7%). There were few differences in prevalence for each age group between sexes, races, and ethnic group. Mean age at onset was 62.6 years (13.1 = SD). ADRD is common in people with ID and individuals, clinicians, and families should be prepared as individuals and populations age. As a heterogenous and often idiopathic group of conditions, further research is warranted to understand biologic and social risk factors for ADRD in this population.