Collections > Electronic Theses and Dissertations > Cognitive Aging in Autism Spectrum Disorder

Little is known about the effects of age on cognitive functioning in adults with autism spectrum disorder (ASD). However, previous aging studies in individuals with Down syndrome, Fragile X, and William’s syndrome suggest accelerated cognitive decline with age. The current study used a cross-sectional design to examine age-related cognitive changes in adults with ASD (ages 30 to 67) compared to adults with typical development (ages 30-65). To examine whether ASD is associated with atypical aging, performance assessed through measures of effortful cognitive processing (known to decline with age) and measures of automatic processing (thought to be relatively age-invariant) were examined. Results indicated that diagnosis was related to poorer cognitive performance. However, aging in ASD was associated with three different patterns of cognitive decline compared to adults with typical development. Adults with ASD exhibited greater age-related decline across three measures designed to assess mild cognitive impairment (e.g., the MoCA), cognitive flexibility [e.g., Trail Making Test (TMT) number-letter switching], and associative learning (e.g., classical conditioning). There was also evidence of similar age-related decline, as compared to controls, on measures of explicit free recall (e.g., RAVLT), visual search (e.g., TMT visual scanning), and processing speed (e.g., TMT number/letter sequencing subtests). Finally, no age-related decline was observed on measures of recognition memory (e.g. RAVLT recognition test), explicit category learning (Woodcock-Johnson Concept Formation), and implicit category learning (e.g., prototype formation). Given different patterns of age-related change observed in adults with ASD, a final multivariate analysis examined overall cognitive performance, including measures of processing speed, cognitive flexibility, executive functioning, explicit category learning, and free recall. Results indicated that when the overall pattern of age-relate cognitive change was considered, age had a disproportionately negative impact on cognitive performance in adults with ASD compared to adults with typical development. These findings suggest aging in ASD may be characterized by greater age-related declines in cognitive functioning, including a particular disruption of executive functions. Theoretical insights are provided by the Processing Resources and Processing Speed theories of cognitive aging, and clinical implications regarding a higher risk for mild cognitive impairment and disruption of pre-frontal cortex are discussed.