Alzheimer dementia in Down's syndrome: the relevance of cognitive ability

More years of education have been found to be associated with a lower rate of Alzheimer disease (AD) in individuals without intellectual disability. I t has been proposed that education reflects greater 'synaptic reserve' and that greater synaptic reserve may defer the development of AD. The present study compared individuals with Down's syndrome (DS) who were found to have symptoms of dementia with those who remained symptom-free to determine if the two groups differed in their level of education, employment, recreation al activities, years in an institution or overall level of cognitive functi oning. Thirty-five adults with DS aged between 29 and 67 years were assesse d. The participants were recruited from a community health facility and inc luded individuals with a wide range of ability levels. Neuropsychological t esting, caregiver report and the Dementia Scale for Down Syndrome (Gedye 19 95) were used to identify decline in participants over periods of 6 months to 3 years. After the effect of age was statistically removed, multiple reg ression analyses revealed that level of cognitive functioning was significa ntly associated with decline such that a higher level of cognitive function ing predicted less decline. None of the environmental variables (i.e. educa tional level, years in an institution and employment) were directly associa ted with decline; however, a post hoc regression using level of cognitive f unctioning as the outcome variable revealed that level of cognitive functio ning itself was associated with these environmental variables. A higher lev el of cognitive functioning was associated with fewer cases of dementia in individuals with DS, and level of cognitive functioning appears to be assoc iated with environmental factors such as level of education, years in an in stitution and employment. The present findings suggest that environmental i nterventions aimed at improving level of cognitive functioning may also be useful in deferring the onset of dementia.