The relation between objective and subjective impairment in cognitive function among multiple sclerosis patients--the role of depression.

Abstract

To evaluate the relations between perceived cognitive function and objective cognitive deficit and to assess variables affecting perceived cognitive function among multiple sclerosis (MS) patients. A cross sectional study of patients with MS. All patients were interviewed and the Expanded Disability Status Scale (EDSS) score was determined. The dependent variables were four items assessing perceived concentration and thinking, attention, memory, and whether others have noticed memory or concentration problems. The explanatory variables were age, sex, duration of disease, number of relapses in the last 2 years, EDSS score, depressive symptoms score (CES-D) and the domains of the Neurobehavioral Cognitive Status Examination (NCSE) assessing cognitive performance. Bivariate and then multivariate analysis were performed. One hundred and sixty-one MS patients were included. Mean age was 44.2 years (s.d. 11.3 years), mean EDSS score was 4.86 (s.d. 1.93). Seventy-two per cent of the patients had objective cognitive impairment and 51% reported decreased perceived cognitive function. In all models assessing perceived cognitive function we could explain only a small part of the variance (R2 ranged between 18-26%). In all these models depressive symptoms explained the highest portion of the variance (partial R2 ranging between 13-26%). The only domain of the NCSE that entered some of the models was calculation (partial R2 ranging between 3-7%). These findings emphasize the gap between objective and subjective assessment of cognitive function and the high correlation between perceived cognitive deficit and depressive symptoms.