Cardiovascular-Cognitive Associations During Physiological Challenges in Relapsing-Remitting Multiple Sclerosis

Cognitive impairment, particularly reduced information processing speed (IPS), is a clinically meaningful manifestation of multiple sclerosis (MS). The Symbol Digit Modalities Test (SDMT) is a sensitive, validated measure of IPS widely used in MS research. While vascular and hemodynamic factors are increasingly recognized as contributors to cognitive performance in MS, their relationship with IPS across distinct physiologic challenges remains unexplored.

This pilot study examined IPS and cardiovascular responses in ten people with MS (PwMS), all of whom had relapsing-remitting MS (RRMS), and ten age- and sex-matched healthy participants during four acute physiologic challenges: head-up tilt, head-down tilt, isometric handgrip, and aerobic cycling.

Beat-to-beat blood pressure and heart rate were continuously recorded; IPS was assessed using the oral SDMT.

Baseline SDMT scores were lower in PwMS than in healthy participants (p < 0.05). A between-group effect was observed for cycling-related SDMT change (r = 0.49, 95% CI 0.05-0.76; p = 0.03). Despite comparable training impulse (TRIMP)-standardized workloads, systolic blood pressure during cycling was higher in PwMS (p < 0.05), and the cycling-related systolic blood pressure response showed a between-group effect of r = 0.46 (95% CI 0.02-0.75; p = 0.04). In healthy participants, baseline SDMT performance was correlated with resting heart rate and blood pressure, and cycling-related SDMT change was inversely correlated with the blood pressure response.

These exploratory findings suggest possible differences in the relationship between cardiovascular measures and IPS during acute physiologic challenges, particularly aerobic exercise. However, the small sample size and wide confidence intervals preclude firm conclusions regarding an exercise-specific effect or differences in cardiovascular-cognitive coupling.