Age-related changes in vestibular function: a longitudinal study.

The objective of this study was to identify age-related changes in the vestibulo-ocular reflex (VOR) in normal older subjects and patients complaining of disequilibrium followed serially over time. Cross-sectional studies have found decreases in vestibular function in older subjects compared to younger subjects, but no prior longitudinal studies have been made following the same older subjects over time. We measured VOR responses using step and sinusoidal stimuli in 110 normal subjects and 51 patients with disequilibrium of unknown cause. This report focuses on 57 normal subjects who were able to return for five yearly examinations and 7 patients who were found to have severe bilateral vestibulopathy on the initial examination. In the normal subjects, there was a significant shortening of the VOR time constant to step changes in angular velocity and an amplitude-dependent decrease in gain and increase in phase lead of low-frequency sinusoidal responses over the five examinations. There was also a decrease in the gain of visual-vestibular responses at low frequencies of sinusoidal stimulation over the five examinations. The patients with bilateral vestibulopathy showed relatively little change in vestibular function over the five years of follow-up. This is the first longitudinal study to show age-related decreases in vestibular responses in normal older subjects. The VOR changes identified were not associated with symptoms or signs of disequilibrium. A small subgroup of patients with disequilibrium of unknown cause had profound bilateral vestibulopathy that remained stable during follow-up. These patients likely had an underlying disease even though in most cases the disease process could not be identified.