Correlation between Cognitive Functions, Fatigue, Depression and Disability Status in a Cohort of Multiple Sclerosis Patients

Abstract

Objective: To investigate the relationship between depression, fatigue, disability and cognitive skills of patients with multiple sclerosis in a cohort of patients with multiple sclerosis in a single center in Tehran, Iran. Methods: One hundred and forty-seven patients with multiple sclerosis with mean age of 33 years, mean disease duration of 20.20 months, mean EDSS of 2.13, and F to M ratio of 76.5% over 23% were recruited for the purpose of this study. Cognitive function was compared with healthy control subjects (n = 100). Depression was measured by Beck Depression Inventory (BDI), fatigue was assessed using Fatigue Severity Scale (FSS) and Modified Fatigue Impact Scale (MFIS), disability was evaluated by Expanded Disability Status Scale (EDSS), and cognitive function was assessed by Brief Repeatable Battery of Neuropsychological tests (BRB-N). All data were analysed using Pearson correlation. Results: Age and disability level generally correlated negatively and significantly with task performance, whereas a higher level of education was associated with better task performance. While the correlation between BDI, FSS, and MIFS was significantly positive, BDI was negatively correlated with the two subscales of BRB, namely PASAT and WLG. Higher levels of depression in patients with MS are associated with lower cognitive performance in tasks requiring higher-order working memory (WM) processes. FSS showed the strongest negative correlation score with BRB, however, the same parameter displayed significant positive correlation with MFIS. Moreover, the global EDSS scores were negatively correlated with BRB. Relative to controls, cognitive performance of MS patients was deficient in all BRB-N measures except Symbol Digit Modalities Test which is a measure of attention and processing speed. Conclusions: Depression, fatigue, and disability (the most common problems observed in MS patients) are clearly related with cognitive impairment in MS patients. Also, MS patients exhibit a pattern of cognitive impairment running across the studied cognitive domains in comparison to healthy subjects.