Imbalance and fractures in the elderly Effects of decreased vibration sensation and vestibular asymmetry

Sammanfattning: Control of the upright stance and locomotion is a complicated process of muscular activity. The muscular activity is dependant on afferent information from the different sensory organs and interpretation in the central nervous system. Age-related degenerative changes exist in all the domains concerned with control of posture. The aims of the studies were to investigate if suspected age-related degenerative changes in sensation perception in lower limbs and vestibular asymmetry among the elderly could be associated with imbalance and fractures. Vibration sensation in the lower limbs was tested with a tuning fork, function of the vestibular organs with a headshake test (video-nystagmoscopy) and postural control with measurements of vibration-induced postural sway (posturography). Results suggested that the majority of elderly subjects had decreased vibration sensation, which did not correlate significantly with increased age. Elderly with intact sensation showed similar balance performance as individuals several decades younger. Elderly with diminished vibration sensation showed greatly reduced balance control compared with elderly with intact sensation and younger adults. The results also implied that elderly subjects had a diminished ability to use visual cues to improve balance control as vision could not fully compensate for proprioceptive impairment. Decreased function of the vestibular apparatus in one ear compared to the other ear (asymmetric vestibular function) was quite common among healthy elderly individuals between 64 and 92 years of age (37%). The frequency of asymmetry was much higher among otherwise healthy elderly of the same age that had previously fallen and sustained a hip fracture (68%). Furthermore, individuals with asymmetric vestibular function demonstrated diminished postural control on posturography. The frequency of asymmetric vestibular function was higher (76%) among people at 50 years of age and older who had recently fallen and sustained a wrist fracture. Many of the hip and wrist fracture subjects had histories of previous falls and fractures mainly seen in the subjects with asymmetric vestibular function. Results of the studies indicate that sensation in the lower limbs plays a major role in balance control. On the other hand, when an individual is confronted with an unexpected postural disturbance, the integrity of the vestibular organs is of significant importance. It is therefore essential to be aware of the sensory status in the lower limbs and the function of the vestibular organs when assessing balance among elderly people. Exercises that combine facilitation to recognize body motion in the lower limbs and inner ear together with fall-reaction training might be beneficial for the aging population especially for individuals with fall-related fractures.