Contribution of auditory inputs to balance in young and older adults

Hypothesis: Traditionally, 3 sensory inputs (visual, vestibular, and somatosensory) are associated with the control of balance and have been investigated for their potential contribution to increased risk of falls. Recent evidence suggests auditory inputs may also contribute to balance control. Although current evidence reveals an association between hearing loss and balance difficulty, the mechanisms behind how and why hearing loss affects balance are unknown. We investigated the contribution of auditory inputs to balance control in healthy young and older adults by simulating hearing loss.Methods: Twenty healthy young and older adults, cleared of any sensory and neurological deficits participated in the study. Participants completed 1 min standing balance, walking, and responding to 10 perturbations at 2m/s² in AP direction while completing a standardized audiology test (BKB-SIN). The audiology test required the subject to repeat back sentences played through the headphones under normal hearing (control) and simulated hearing loss conditions, randomly assigned. Simulated hearing loss was achieved using a pair of Bose QuietComfort 35 wireless noise-cancelling headphones. Adobe Audition was used to simulate moderate hearing loss. Outcomes included: Center of Pressure (COP) sway variability, number of compensatory steps, COP-COM during first compensatory step after perturbation, performance of auditory task, and self-selected gait speed. Clinical physical therapy outcome measures were also administered. ANOVA was conducted for each of the dependent variables with respect to group and condition of auditory task.Results: Compared to normal hearing, simulated hearing loss resulted in significantly increased COP sway variability significantly and more compensatory steps in response to perturbations in older adults. Preliminary results showed that in response to surface perturbations, the COP-COM distance was an average of 25cm and 15cm in young and older adults, respectively, reflecting the shorter, multiple steps taken by older adults.Conclusions: Simulated hearing loss negatively impacts postural control particularly in dual-task conditions when individuals simultaneously attend to auditory and postural tasks. The effect is stronger in older adults who have fewer resources to compensate for poor sensory input. Individuals with hearing loss may be at greater risk of falling than individuals without hearing loss.