Subjective cognitive fatigability is associated with worse patient-reported physical disability in multiple sclerosis.

Background: Fatigue is highly prevalent in multiple sclerosis (MS) and contributes to disability and functional decline. While associations between physical fatigue and disability have been well characterized, how subjective cognitive fatigue and fatigability relates to disability in MS remains understudied.

Methods: People with MS (PwMS; N = 100) completed self-report measures to capture secondary disease characteristics (e.g., mood, sleep, subjective cognitive fatigue and fatigability). The outcome variable was self-reported disability status (as measured by the Patient Determined Disease Steps). Multiple regressions with an exhaustive search of the model space were conducted to test associations between secondary disease characteristics and self-reported disability status.

Results: PwMS with high subjective cognitive fatigability (n = 42) were more disabled (p = .006) and reported worse depressive symptoms, perceived cognitive impairment, subjective cognitive fatigue, sleep quality, and unemployment (ps<0.002) compared to PwMS with low subjective cognitive fatigability (n = 43). Subjective cognitive fatigability (p = .002) and age (p < .001) emerged as the best fitting indicators of disability status.

Conclusions: Subjective cognitive fatigability was a stronger indicator of self-reported physical disability than subjective cognitive fatigue, sleep, and mood. Screening for and reducing cognitive fatigability may improve patient-report disability in PwMS.