Brain activation in high-functioning older adults and falls Prospective cohort study

Objective: To determine whether brain activity over the prefrontal cortex measured in real time during walking predicts falls in high-functioning older adults. Method: We examined166 older persons (mean age 75 years, 51% women) enrolled in a prospective aging study. High-functioning status defined as the absence of dementia or disability with normal gait diagnosed by study clinicians. The magnitude of task-related changes in oxygenated hemoglobin levels over the prefrontal cortex was measured with functional near-infrared spectroscopy during motor (walking at normal pace) and cognitive (reciting alternate letters of the alphabet) single tasks and a dual-task condition (walking while reciting alternate letters of the alphabet). Incident falls were prospectively assessed over a 50-month study period. Results: Over a mean follow-up of 33.9 +/- 11.9 months, 116 falls occurred. Higher levels of prefrontal cortical activation during the dual- task walking condition predicted falls (hazard ratio adjusted for age, sex, education, medical illnesses and general mental status 1.32, 95% confidence interval 1.03-1.70). Neither behavioral outcomes (velocity or letter rate) on the dual task nor brain activation patterns on the single tasks (normal walk or talk alone) predicted falls in this high-functioning sample. The results remained robust after accounting for multiple confounders and for cognitive status, slow gait, previous falls, and frailty. Conclusions: Prefrontal brain activity levels while performing a cognitively demanding walking condition predicted falls in high-functioning seniors. These findings implicate neurobiological processes early in the pathogenesis of falls.