Changes in adaptive functioning of adults with developmental disabilities

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Abstract
Adaptive behavior skills of 2,144 adults with Down syndrome aged 20–69 years were compared to those of a matched group of 4,172 developmentally disabled people without Down syndrome. Adaptive competence in eight skill domains was examined as a function of etiology, age-group and level of mental retardation. In all behavioural domains, and at all levels of mental retardation, individuals with Down syndrome displayed significantly more age-related deficits than did age-matched controls. In individuals with Down syndrome, substantial age-related deficits in adaptive competence were observed after 49 years of age and were most pronounced after 59 years of age. Our findings support previous suggestions of increased risk for Alzheimer disease among adults with Down syndrome. However, Alzheimer neuropathology is found in people with Down syndrome by 40 years of age; signs of regression in adaptive behavior occur 10–15 years after the presumed onset of pathological processes. These results may suggest that the processes underlying dementia in individuals with Down syndrome can have an extremely prolonged course.