Towards healthy aging: Quantifying vestibular contributors to age-related changes in balance and fall risk

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Imbalance contributes to falls, fall risk increases with age, and falls cause accidental death and injury. While causes of falls and imbalance are multifactorial, modern multivariate statistical analyses allow us to quantify the impact of age-related vestibular declines on falls as well as the impact of age-related vestibular declines on age- related balance declines. For example, we have recently reported that nearly 50% of cross-sectional age-related balance declines found using a standard Romberg test variant (“eyes closed; standing on foam”) are mediated by an age-related increase in roll tilt thresholds, suggesting that a single sub-clinical facet of vestibular function is a substantial contributor to age-related balance declines. Furthermore, an analysis of over 5,000 Americans showed that individuals who failed to complete this same balance test condition had significantly increased odds to have reported “difficulty with falling” in the past 12 months (odds ratio of 6.3). We propose to build upon these findings to quantify the multiple links between aging, vestibular function, balance, and falls. We posit the following links: (i) vestibular function declines with age, (ii) these age-related vestibular declines impact balance, (iii) imbalance contributes to falls, and (iv) falls cause death and injuries. Specifically, we posit that correlations between aging, vestibular function, and balance arise, in part, because vestibular imprecision (i.e., vestibular thresholds or vestibular “noise”) increases with age as demonstrated by large increases in vestibular thresholds above the age of 40. Increased vestibular imprecision, in turn, contributes to instability, which contributes to falls. To quantify these correlations and hypothesized causal links, we propose comprehensive assays of vestibular function, broad multi-faceted balance assays, as well as reports of falls. We also propose to further develop and test candidate interventions designed to improve tilt thresholds (“vestibular precision”), which could also improve balance and reduce falls. Given life-or-death significance and broad impact, we propose: Aim 1: To quantify the links between age, vestibular function, balance, and falls in healthy individuals using a comprehensive vestibular function test battery, broad multi-faceted balance tests, & fall-related surveys. Aim 2: To quantify both tilt thresholds and balance before and after a training intervention that has subjects performing a standard tilt threshold task, except that feedback (“correct” or ”incorrect”) is provided after each trial. This task is designed to improve vestibular thresholds (“precision”), which may also improve balance. For Aim 2A, we propose to test young adults (age 18-40). For Aim 2B, we propose to test older adults (age 65-89). Aim 1 will quantify links between vestibular function and falls for the first time and will also quantify new links between vestibular function and balance. This will define potential vestibular and/or balance tests that can be used as screening tests to determine who would benefit from intervention. Aim 2 will quantify the impacts of a training paradigm designed to reduce tilt thresholds. This will develop and test an intervention designed to improve vestibular precision, which could also improve balance and reduce falls.