Risk factors for dementia in people with down syndrome: issues in assessment and diagnosis.

It has been clearly established that there is an increased incidence of early onset dementia of the Alzheimer type (DAT) in people who have Down syndrome. There are variations in the age of onset of the clinical signs of DAT, which may be accounted for by different risk factors. In this review we examined the evidence that different biological and psychological factors may influence the risk for DAT. Limitations in design of early studies, the need for consistent diagnostic criteria for DAT in individuals with Down syndrome, and the lack of adequate psychometric tools to detect cognitive change are highlighted. Implications for research and clinical practice are considered in order to assess potential risk factors.