People with multiple sclerosis (pwMS) commonly describe cognitive decline later in the day, but few studies have evaluated this perception's validity. In a consecutive sample of 791 pwMS, this study evaluated whether time-of-testing predicted Minimal Assessment of Cognitive Function in MS raw scores, accounting for age, sex, educational years, disease duration, disability and disease-modifying therapy use. The mean age was 43.76 years (SD = 11.30), 76.74% were female and most had mild disability. Later time-of-testing independently predicted reduced Judgment of Line Orientation scores (p < 0.01), but not other cognitive variables. In pwMS, there is a diurnal decline in visuospatial cognitive test performance.
Keywords: Multiple sclerosis; cognition; neuropsychology; outcome measurement; time of day; time-of-testing.