Causes of age-related decline in adaptive behavior of adults with Down syndrome: differential diagnoses of dementia.

Although a decline in adaptive behavior with age in adults with Down syndrome has been established, the underlying causes of the decline remain unresolved. Differential causes of the decline in 201 adults with Down syndrome were investigated. Aging, dementia, and severity of mental retardation were found to be significant factors. Absence of a medical illness was a factor that predicted a higher level of adaptive behavior. No significant difference in age-related maladaptive behaviors was found. However, a clinical diagnosis of dementia was a predictive factor for increased maladaptive behavior. Clinical implications of these findings were discussed.