Reliability and validity of the psychomotor vigilance task to quantify cognitive fatigability in multiple sclerosis

Cognitive fatigability is a decline in performance over the course of a sustained cognitive task. Objective, time-efficient, and reliable measures of cognitive fatigability remain limited. The Psychomotor Vigilance Task (PVT) has been utilized to quantify sustained attention deficits, but its psychometric properties for MS populations are not well established.

To evaluate the reliability and validity of a 10-minute PVT of cognitive fatigability in MS patients.

Twenty-two MS patients completed the 10-minute PVT on three occasions, 7-10 days apart. Cognitive fatigability was quantified as performance decline across five consecutive 2-minute blocks using reaction time (RT) and cognitive lapses. Cognitive lapses were analyzed using a ≥ 500-ms and ≥300-ms thresholds. Test-retest reliability was assessed using intraclass correlation coefficients (ICC). Convergent validity was assessed by associations between PVT indices (RT and cognitive lapses) and general cognitive fatigue, and current fatigue. Divergent validity was assessed by associations between PVT indices and global cognition and cardiorespiratory fitness.

Across all sessions, participants demonstrated slowing of RT, indicating cognitive fatigability. Cognitive lapses increased over time when the ≥300-ms was applied. Test-retest reliability was excellent for mean RT (ICC=0.934), median RT (ICC=0.928), and cognitive lapses (≥500-ms [ICC=0.925] and ≥300-ms [ICC=0.829]). RT (r = 0.621) and cognitive lapses using the 500-ms (r = 0.477) and 300-ms (r = 0.560) were associated with cognitive fatigue. Neither RT nor cognitive lapse was associated with current fatigue, global cognition, or cardiorespiratory fitness.

The 10-minute PVT, using RT and cognitive lapses, is a brief measure of cognitive fatigability in MS for clinical evaluation in MS fatigue.