Our Research Lab
Aldosterone and Age-Related Hearing Loss
Several earlier investigations have indicated a significant relationship between measured levels of the steroid hormone aldosterone (ALD) and several aspects of age-related hearing loss in both humans and in animal models. The aims of this research are to establish possible relationships between auditory function, auditory perception, and ALD in a cross-sectional and longitudinal research design in older human adults. One hypothesis is that a deficiency in the concentration of ALD concentration could be related to changes in hearing sensitivity or auditory function.
Aldosterone (ALD) is a steroid hormone secreted by the adrenal glands and plays an important role in regulating sodium (Na+) and potassium (K+) levels and reabsorption of water in the kidneys. In addition, ALD contributes to cochlear homeostasis by regulating Na+ and K+ levels through Na/K-ATPase in the stria vascularis.
Cross sectional studies have shown that ALD levels gradually decline as we age. Both animal and human studies have shown a significant positive relationship between hearing performance, auditory function and ALD levels, but little is known about how the relationships change over time. Unfortunately, lower ALD concentrations have been associated with the degeneration of inner ear cells while higher ALD concentrations have been associated with better hearing sensitivity. One possibility is to supplement ALD levels, boosting them to the upper end of the normal range, to protect hearing as we age. Thus, it is promising that this research could lead us to the first treatment for age-related hearing difficulty.
The goal of this longitudinal study is to characterize the relation between auditory function and ALD levels in older adults over time. Based on previous studies, we hypothesize that higher ALD levels will correlate with lower hearing thresholds, better hearing-in-noise performance, and more robust physiological responses.
Key measures in this study include serum aldosterone levels and other metaboloic indices as well as behavioral and physiological measures of hearing that are known to change with age. Those include perceptual measures of speech recognition in background noise, temporal fine structure and temporal envelope coding, and binaural hearing - all assayed via listening experiments. We also index peripheral and brainstem auditory function with otoacoustic emission, click ABR, and speech ABR measures. At the end of the study, we will have documented changes in ALD with age within and across participants over a four-year period. At the same time, we will have documented changes in auditory perception and function in the same manner. Together, these will help determine any relationships between ALD and ALD change and the auditory system.