Analyze the association between performance on speeded and nonspeeded tasks of executive functions (EFs) and slow information processing speed (IPS) in people with Multiple Sclerosis (PwMS).

IPS and EFs are impaired domains in PwMS. However, it is unclear if executive deficits can be explained by slow IPS. 

74 PwMS were included (RR=86.2%, PP=4.3%, SP=9.6%; 74% female; age: 46.12±12.48 years; Physical disability (EDSS): 3.60±2.57; disease duration: 14.85±10.69 years). Measures: IPS: Symbol Digit Modalities Test; EFs: Speeded task of cognitive flexibility (Verbal Fluency), nonspeeded task of cognitive flexibility (Brixton Spatial Anticipation Test), nonspeeded task of working memory (Verbal Backward Digit Span); Clinical variables: EDSS, Fatigue Severity Scale and Beck Depression Inventory-II. A probit regression was performed, the results are shown in predicted probabilities format.

47% of PwMS have slow IPS. IPS was associated with EDSS and all EFs measures (p=0.00) and did not correlated with fatigue and depression (p>0.05). For the regression model, IPS, EDSS and EFs tasks were analyzed. Brixton and backward span tests lost significance when physical disability was controlled. Finally, the regression model had verbal fluency (Coefficient:-.49;p=0.001) and physical disability (Coefficient:.21; p=0.02) as independent variables. R²28%. Prob.chi2=0.00. For the predicted probabilities, verbal fluency was divided into 4 groups, controlling physical disability, and it was found that the probability of having poor verbal fluency with poor IPS is very high in the 1st and 2nd groups (.89 and .68, lowest confidence interval 0.53) and the probability of having high verbal fluency and slow IPS is very low in the 3th and 4th groups (.38 and .14, highest confidence interval 0.50), with no overlapping confidence intervals. Correctly classified 72%.