The Mediating Role of Cognitive Fatigue on the Relationship Between Anxiety and Illness Intrusiveness in Multiple Sclerosis Patients

Background:

Cognitive fatigue is a physiological fatigue phenomenon that is a common subjective complaint in Multiple Sclerosis. Research has found that cognitive fatigue is associated with increased feelings of illness intrusiveness. Anxiety is common among individuals living with MS, with prevalence rates ranging from 19% to 57%. Anxiety in the MS population has been found to be associated with depression, pain, fatigue, stress, and lower self-efficacy and quality of life. Research has shown that anxiety in the general population is also associated with impairment in cognition, particularly in processing speed and attention. Recent research also suggests that anxiety is associated with increased illness intrusiveness in MS. 

Objectives:

The present study evaluates the mediating relationship of cognitive fatigue on the relationship between anxiety and illness intrusiveness in patients with MS.

Methods:

Data was collected from 124 MS patients who underwent full neuropsychological evaluation at the MS Center at Holy Name Medical Center in Teaneck, NJ. Anxiety was measured using the self-report measure, Hospital Anxiety and Depression Scale (HADS). Illness instrusivenss was measured using the llness Intrusiveness Ratings Scale (IIRS), a 13-item, self-report instrument measuring relationships and personal development, intimacy, and instrumental intrusiveness. Cognitive fatigue was measured using the cognitive subscale of The Fatigue Scale for Motor and Cognitive Functions (FSMCC). All of the measures have been well-validated in the MS population. Mediation analysis was run with Process, by Hayes using SPSS 24.0 to test the hypothesized relationship. Specifically, anxiety was entered as the predictor variable, illness intrusiveness as the outcome variable, and cognitive fatigue as the mediating variable. 

Results:

Results indicated that anxiety was a significant predictor of cogntive fatigue, b = 1.138, SE = 1.574, p < .001, and that cognitive fatigue was a significant predictor of illness intrusiveness, b = .0415, SE = .0098 p < .001. These results support the mediational hypothesis, consistent with partial mediation. Approximately 57% of the variance in illness intrusiveness was accounted for by anxiety and cogntive fatigue (R²= .5723).

Conclusions:

Statistical analyses support the hypothesis that cognitive fatigue is a significant mediator in the relationship between anxiety and illness intrusiveness. Particularly, anxiety was associated with increased cognitive fatigue, which in turn, was associated with increased illness intrusiveness. Cognitive fatigue was a partial mediator.