Predictors of performance and perceived fatigability in people with multiple sclerosis.

Background And Objective: Fatigability is a distinct construct from fatigue that has been reported to contribute to activity limitations in people with multiple sclerosis (PwMS). Identifying predictors of performance and perceived fatigability may guide the development of interventions to mitigate fatigability. This study investigated predictors of performance and perceived fatigability among PwMS.

Methods: PwMS ( = 51) completed self-report measures of demographics, clinical history, symptoms severity (Modified Fatigue Impact Scale), and functioning (PROMIS Physical Function and PROMIS Cognitive Function Abilities). Performance fatigability measures included Ambulatory Fatigue Index (AFI), Deceleration Index (DI), and Distance Walking Index (DWI). Perceived fatigability measures included Pittsburgh Fatigability Scale (PFS), Perceived Physical Exertion, and Perceived Fatigue Intensity. Performance and perceived fatigability measures were calculated based on the Timed 25-Foot Walk Test and the 6-Minute Walk Test.

Results: Multivariable linear regression analyses indicated that PROMIS Cognitive Function was a significant independent predictor of performance fatigability measured with AFI (β = -0.515,  = 0.007), DI (β = -0.511,  = 0.008), and DWI (β = -0.516,  = 0.007). Regarding perceived fatigability, PROMIS Pain Intensity predicted Perceived Fatigue Intensity (β = 0.325,  = 0.035). PROMIS Physical Function predicted PFS Mental fatigability (β = -0.503,  < 0.001). PROMIS Physical Function (β = -0.619,  < 0.001) and Cognitive Function (β = -0.249,  = 0.037) predicted PFS Physical fatigability.

Conclusions: Preliminary findings suggest that self-reported functioning levels, including physical and perceived cognitive function, are potential predictors of performance and perceived fatigability in MS. Notably, perceived fatigue impact showed no association with performance or perceived fatigability. Future studies are warranted to confirm and extend our findings.