Incidence and course of dementia in people with Down's syndrome: findings from a population-based study

The prevalence rate of Alzheimer's disease (AD) in people with Down's syndr ome (DS) increases significantly with age. However. the nature of the early clinical presentation, course and incidence rates of dementia are uncertai n. The aims of the present study were to investigate the characteristics of age-related clinical changes and incidence rates for dementia in a populat ion-based sample of people with DS aged 30 years and older at the age of ri sk for dementia. A modified version of the Cambridge Examination for Mental Disorders of the Elderly informant inter-view was used to determine the ex tent and nature of changes in memory, personality, general mental functioni ng and daily living skill 18 months after a similar assessment At the time of the firn assessment, the initial changes reported were predominately in behaviour and personality. At the second assessment, overall estimated inci dence rates for frontal-like dementia were high (0.24), mainly in the young er groups, with incidence rates of AD. meeting both ICD-10 and DSM-IV crite ria, of 0.04 predominately in the older groups. The present authors have hy pothesized that the observed personality changes and the high estimated inc idence rates of frontal-like dementia in the younger groups may indicate th at functions served by the frontal lobes are the first to be compromised wi th the progressive development of Alzheimer-like neuropathology in people w ith DS.