Sense of Balance

Many of the changes in balance function in older adults may be due to deterioration in the different sensory systems contributing to balance, including the somatosensory (cutaneous and proprioceptive), visual, and vestibular (inner ear) systems. Tactile sensitivity decreases with age. Research examining reactive balance control in patients with peripheral neuropathy has found delays in muscle onset latencies in response to platform perturbations.

Age-related changes in the influence of vision on balance control can be tested by creating the illusion of postural sway through visual flow generated by an experimental moving room. Normally, young adults show small amounts of sway in response to visual flow, since their proprioceptive systems indicate no sway. However, healthy older adults respond to visual flow with increased sway, and balance-impaired older adults show the most visually induced sway of the three groups. This may be due to decreased somatosensory information available for balance in older adults, due to peripheral neuropathy.

Research on age-related reduction in the function of the vestibular system indicates a loss of 40 percent of the vestibular hair and nerve cells by seventy years of age. The vestibular system contributes to the amplitude of postural responses to balance threats, and thus, older adults with vestibular loss would show inappropriately small responses to balance threats. The vestibular system serves as an absolute reference system to which the other systems (visual and somatosensory) may be compared and calibrated, and is thus critical for optimal balance function.

Figure 1 Balance statistice for a young adult; a stable older adult; and an unstable older adult. SOURCE: Author