Down's syndrome: intellectual and behavioural functioning during adulthood

Previous cross-sectional studies of Down's syndrome have suggested that deficits in cognitive and neurological functioning after the age of 35 years are symptomatic of Alzheimer's disease. It has been claimed that this pattern corresponds to post-mortem neuropathological findings of Alzheimer's disease in all Down's syndrome patients who die aged over 35 years. In the present study of Down's syndrome patients aged between 19 and 49 years, results showed that, for those over 35 years, intellectual deterioration had occurred in less than a third. No relationship was found between chronological age and the level of self care skills or the presence of disturbed behaviour. Results are discussed in terms of the interpretation of the existing neuropathological literature, the methodology of future studies and clinical decisions regarding hospitalized patients with Down's syndrome.