Brain hemodynamic responses and fall prediction in older adults with multiple sclerosis.

OBJECTIVE We examined whether brain hemodynamic responses, gait, and cognitive performances under single- and dual-task conditions predict falls during longitudinal follow-up in older adults with multiple sclerosis (OAMS) with relapsing-remitting and progressive subtypes. METHODS Participants with relapsing-remitting (n = 53, mean age = 65.02 ± 4.17 years, %female = 75.5) and progressive (n = 28, mean age = 64.64 ± 4.31 years, %female = 50) multiple sclerosis (MS) subtypes completed a dual-task-walking paradigm and reported falls during longitudinal follow-up using a monthly structured telephone interview. We used functional near-infrared spectroscopy (fNIRS) to assess oxygenated hemoglobin (HbO) in the prefrontal cortex during active walking and while performing a cognitive test under single- and dual-task conditions. RESULTS Adjusted general estimating equations models indicated that higher HbO under dual-task walking was significantly associated with a reduction in the odds of reporting falls among participants with relapsing-remitting (odds ratio (OR) = 0.472, p = 0.004, 95% confidence interval (CI) = 0.284-0.785), but not progressive (OR = 1.056, p = 0.792, 95% CI = 0.703-1.588) MS. In contrast, faster stride velocity under dual-task walking was significantly associated with a reduction in the odds of reporting falls among progressive (OR = 0.658, p = 0.004, 95% CI = 0.495-0.874), but not relapsing-remitting (OR = 0.998, p = 0.995, 95% CI = 0.523-1.905) MS. CONCLUSION Findings suggest that higher prefrontal cortex activation levels during dual-task walking, which may represent compensatory reallocation of brain resources, provide protection against falls for OAMS with relapsing-remitting subtype.