Conceptual reasoning as a mediator of verbal recall in patients with multiple sclerosis.

A number of intercorrelated factors, including level of neurologic impairment, age, and conceptual reasoning, appear to be related to memory performance among patients with Multiple Sclerosis (MS). A battery of neuropsychological tests was administered to 131 patients with MS ranging in age from 19 to 76 years, with a mean symptom duration of 12.3 years and an overall mild level of MS-related neurologic impairment. Regression analyses indicated that neurologic impairment and age each contributed uniquely to the prediction of delayed free recall of a word list. Furthermore, when the effect of conceptual reasoning was accounted for, neither neurologic impairment nor age were significantly related to recall. Thus, a mediated relation was confirmed, supporting the idea that a significant portion of neurologic-impairment-related and age-related differences in recall are due to differences in conceptual reasoning that are important for optimal performance on tests of recall. Additional analyses failed to support a similar mediated relation using recognition rather than recall as the measure of memory performance.