How's Your Balance?

Preserving sensory function, particularly in the feet, is essential for preventing falls and maintaining autonomy and health across the human lifespan. Monofilament testing is a widely used clinical tool for assessing foot sensation. In older adults, this test typically involves applying a standardized nylon filament (commonly the 10g monofilament) to specific sites on the plantar surface of the foot. Loss of sensation detected through monofilament testing often indicates peripheral neuropathy, which can be caused by aging, diabetes, or other conditions affecting nerve function. This sensory impairment significantly impacts postural control by reducing the afferent feedback needed for postural adjustments. Thus, monofilament testing serves as a diagnostic tool and a predictor of fall risk, emphasizing the critical role of sensory feedback in maintaining stability and preventing injury in aging populations.

In addition to monofilament testing, single leg stance time is a strong indicator of balance, functional, and neurological health, with shorter times signaling higher fall risks, particularly in older adults. The unipedal or single leg (limb) stance test measures static postural control and is a valuable, quick screening tool in clinical settings to identify individuals in need of further evaluation or rehabilitation. Inability to hold a one-leg stand for at least 5 seconds is a red flag for potential balance issues, while a 30-second hold indicates good stability. We will expand on existing research by examining plantar sensitivity across ages and exploring links between fall history, unipedal stance time, and plantar cutaneous sensation.

Primary Research Question/Hypothesis What is the relationship between physiological aging and Romberg ratio values during standing balance, and how well can age and somatosensory function explain variation in Romberg ratio values? We hypothesize that older age and reduced somatosensory function will be associated with higher Romberg ratio values (i.e., stronger dependence on vision, suggestive of somatosensory deficits) during standing balance.

Secondary Research Question(s)/Hypothesis

• To what extent does plantar cutaneous sensitivity at different foot sites relate to Romberg ratio values during standing balance, and which site(s) remain significant predictors after controlling for age? We believe that reduced plantar cutaneous sensitivity (higher monofilament thresholds) at medial foot sites will be associated with higher Romberg ratio values, independent of age.
• How are standing Romberg ratio values related to self-reported physical function (PROMIS® PROWalk™) and balance confidence (ABC-6) across different ages? We hypothesize that self-reported physical function and balance confidence will be significant predictors of standing Romberg ratio values, such that lower PROMIS® PROWalk™ scores and lower ABC-6 scores are associated with higher Romberg ratio values, independent of age.
• We will continue to evaluate whether the threshold for loss of balance sensation is lower than that for loss of protective sensation (i.e., inability to feel a 10g monofilament at 2 of 5 sites on the plantar surface of the foot). We hypothesize that impaired balance will be associated with reduced or absent plantar cutaneous sensation, regardless of age.