The influence of age and lutein status on vestibular and auditory function
Wong, Jennifer Caroline
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Increased oxidative stress may promote increases in neural noise. One immediate defense mechanism for increased oxidative stress is to accumulate exogenous antioxidants, such as the dietary carotenoids. Lutein (L) and zeaxanthin (Z) are two carotenoids found in the macular pigment (MP) and outer layers of the lens. Retinal levels of LZ are positively correlated with levels of LZ in the auditory cortex and cerebellum, regions important for auditory and vestibular function, respectively. The purpose of these studies was to examine (using both longitudinal and cross-sectional designs) the relationship between age, indices of oxidative exposure (MP density, lens density), and sensory function (vestibular and auditory). MP and lens density were assessed psychophysically with a non-invasive method. Vestibular function was assessed with the One Foot Balance test. Auditory function was assessed with a Grason-Stadler Instruments 61 two channel instrument (GSI 61) using the Modified Hughson-Westlake method. Two elderly groups participated in the longitudinal arms of this study. MP density was available for one group that was tested 11 years earlier (N = 12, M = 74.5 ± 9.1 years). MP density was significantly (p < .001) higher at the second time point. Vestibular function was also assessed longitudinally. These measures, along with MP density, were available across an eight year time period (N = 7, 70.3 ± 4.4 years). Vestibular function was significantly (p < .05) higher when assessed at the second time point. MP density was not associated with individual baseline or follow-up vestibular assessments. Fifty non-smokers and 17 smokers, across ages, participated in the cross-sectional study. Age was significantly related to all variables: vestibular and auditory function and MP and lens density. When stratified by age and smoking status, MP density and lens density were significantly related to auditory function only in young healthy individuals.