Diagnosing dementia in adults with Down's syndrome.

Individuals with Down's syndrome (DS) are living longer and many will survive into their fifth or sixth decade of life. Among the DS population, the prevalence of dementia in Alzheimer's disease increases from 9.4% in age group 30-39 years to 54.5% age group 60-69 years. The psychopathology of dementia in Alzheimer's disease is similar to that seen in the general population although differences are apparent due to the underlying intellectual disability in DS and on the reliance on collateral information from informants. The diagnostic workup follows accepted practice although neuropsychological tests and neuroimaging will only be adjuncts to the clinical assessment; such investigations have limited diagnostic value. Presently, research is focused on identifying genetic and biological measures of Alzheimer's disease in DS.