The Complex Interplay Between Trait Fatigue and Cognition in Multiple Sclerosis

Abstract

Cognitive impairments are frequent in patients with Multiple Sclerosis (MS). Yet, the influence of MS-related symptoms on cognitive status is not clear. Studies investigating the impact of trait fatigue along with anxio-depressive symptoms on cognition are seldom, and even less considered fatigue as multidimensional. Moreover, these studies provided conflicting results. Twenty-nine MS patients and 28 healthy controls, matched on age, gender and education underwent a full comprehensive neuropsychological assessment. Anxio-depressive and fatigue symptoms were assessed using the HAD scale and the MFIS, respectively. Six composite scores were derived from the neuropsychological assessment, reflecting the cognitive domains of working memory, verbal and visual learning, executive functions, attention and processing speed. Stepwise regression analyses were conducted in each group to investigate if trait cognitive and physical fatigue, depression and anxiety are relevant predictors of performance in each cognitive domain. In order to control for disease progression, patient's EDSS score was also entered as predictor variable. In the MS group, trait physical fatigue was the only significant predictor of working memory score. Cognitive fatigue was a predictor for executive functioning performance and for processing speed (as well as EDSS score for processing speed). In the healthy controls group, only an association between executive functioning and depression was observed. Fatigue predicted cognition in MS patients only, beyond anxio-depressive symptoms and disease progression. Considering fatigue as a multidimensional symptom is paramount to better understand its association with cognition, as physical and cognitive fatigue are predictors of different cognitive processes.

Keywords: Anxiety; Cognition; Depression; Fatigue; Multiple Sclerosis.

Figure 1

Illustration of regression lines in MS patients and healthy controls for variables included in significant models. Data points and regression lines for (A) working memory index depending on physical fatigue (physMFIS), (B) executive functioning z-score depending on cognitive fatigue (cogMFIS), (C) executive functioning z-score depending on depression (HAD Depression), (D) processing speed index depending on cogMFIS and (E) processing speed index depending on EDSS (Expanded Disability Status Scale) score for MS patients. Healthy controls are depicted in light blue circles, MS patients in dark blue triangles.