Cognitive aging in patients with multiple sclerosis: a cross-sectional analysis of speeded processing.

Studies have identified generalized slowing in information processing speed as the primary cognitive deficit in multiple sclerosis (MS). Similar changes are also commonly observed in healthy cognitive aging. The present study is the first to examine the combined impact of aging and disease on the course of cognitive slowing. MS patients (N = 245) and healthy controls (N = 188) were assessed using two measures of processing speed (the preliminary word reading and color naming trials of the Stroop). Participants ranging in age from 18 to 74 were grouped into five age cohorts. Slowing in processing speed was evident for patients vs. controls and for older vs. younger cohorts. The age-related declines in performance were parallel for patients and controls, indicating that the disease process in MS does not interact with general cognitive aging to effect a more rapid decline in functioning.