Tinnitus, Hearing Impairment and Diabetes: A Mini-Review.
Tinnitus is one of the three most significant otoneurological clinical manifestation besides sensorineural hearing impairment and vertigo. About 44 million American adults experience the condition of tinnitus. Of those affected, approximately 1 million consider themselves significantly debilitated as a result.
The United Nations estimates the number of people globally affected by diabetes to be 246 million. Approximately, 17 million Americans suffer from diabetes.4 Diabetes is a metabolic disorder in which the body cannot metabolize glucose characterized by symptoms such as hyperglycemia and alterations in protein and fat metabolism. Hyperglycemia may arise due to the inability of the pancreas to produce insulin as seen in type 1 diabetes or due to the failure of the body to properly utilize insulin commonly observed in type 2 diabetes. Both of these conditions lead to high glucose levels in the blood.
Microangiopathy also affects the cochlear vessels of the ear. Studies on diabetes-induced animals
have shown that such microvascular changes might occur in the inner ear as well which may disrupt the flow of circulation, result in the narrowing of capillaries, and lead to the loss of outer hair cells, which is responsible for the amplification of the sound entering the cochlea. This may lead to a complete depletion of nutrients, cell degeneration, and atrophy. Degeneration of nerve
cells is observed in both the cochlea and the eighth nerve. The atrophy of outer hair cells in the organs of cortii may also result. Tinnitus as a symptom is mostly observed in disorders involving metabolic disturbances and diabetes mellitus.
The metabolism of the inner ear depends on the oxygen and glucose supply from the blood circulation. Alterations in the glucose metabolism can thereby disturb the function of the brain cells and the inner ear; which may lead to reduced processing of complex sounds as speech and contributes as a cause of occurrence of tinnitus with hearing impairment. Tinnitus may have various debilitating effects on the sufferer.
Otolaryngol Open J. 2017; SE(5): S6-S9. doi: 10.17140/OTLOJ-SE-5-102