SLC6A3 and dementia: Two recent cross sectional studies on cognition in adults with Down syndrome without dementia reflect our observation that in older adulthood, most individuals with Down syndrome may already show significant cognitive deficits associated with DAT, reporting a significant age-related decline in cognitive function and social adaptation skills [48] and lower neuropsychological function and adaptive skills in adults with Down syndrome over 40 years old, compared to those under 40 [49].