Abstract
The prevalence and incidence of early-onset dementia among adults with autism spectrum disorder (ASD) is currently unknown. In this case-control study, the prevalence and incidence of early-onset dementia in individuals with ASD was examined during 2008-2012 using Medicaid Analytic eXtract files. Participants were 30-64 year-old adults who were Medicaid beneficiaries and had either a diagnosis of ASD only (n = 12,648), a diagnosis of ASD with co-occurring intellectual disability (ID) (n = 26,168), a diagnosis of ID without ASD (n = 406,570), or no ASD nor ID diagnoses (n = 798,828). The 5-year prevalence of dementia was 4.04% among adults with ASD only, and 5.22% for those with ASD and co-occurring ID. This prevalence was higher compared to the prevalence of dementia in individuals with no ASD and no ID (0.97%), but lower compared to individuals with ID only (7.10%). Risk factors associated with the increased prevalence in the general population were similarly associated with the increased risk of dementia in individuals with ASD. Even after adjusting for these risk factors, compared to the general population, dementia was found to occur more frequently in individuals with ASD only (adjusted hazard ratio, 1.96; 95% CI, 1.69-2.28), as well as individuals with ASD and co-occurring ID (adjusted hazard ratio, 2.89; 95% CI, 2.62-3.17). In conclusion, adults with ASD under the age of 65 were approximately 2.6 times more likely to be diagnosed with dementia compared to the general population in our study. LAY SUMMARY: It is unclear whether adults diagnosed with autism spectrum disorder (ASD) are at higher risk of being diagnosed with early-onset dementia compared to those who are not on the autism spectrum. In this study we examined for the first time the nationwide prevalence and incidence of Alzheimer's Disease and other types of dementia in ASD in a sample of adults with ASD aged 30-64 years who were enrolled in Medicaid, the largest insurer of behavioral health services in the US. Medicaid claims data, which include information on the diagnoses that beneficiaries receive, suggested that the adults with ASD were approximately 2.6 times more likely to be diagnosed with early-onset Alzheimer's disease and related dementias compared to the general population.