https://pubmed.ncbi.nlm.nih.gov/34378867/

There have been several small, or small-ish, studies looking at the link between dementia and autism or ID. However, recently, the largest medical record study of 500k people, 12k of which were autistic and 26k were autistic and had ID, examining early onset dementia was published. Those with ASD had a 1.9 increased risk for dementia and it was even higher for those with ASD + ID. Why? Is it psychological or biological or both? Researchers at the AJ Drexel Autism Institute investigate.