Diabetes mellitus is a multisystem disorder related to carbohydrate metabolism which occurs because of absolute or relative insulin deficiency. Along with metabolic disturbance various pathologic changes in the human body are associated with diabetes. The disorder is characterized by evaluated blood sugar levels and abnormalities in insulin secretion, which leads to alteration in metabolism of carbohydrates, proteins, and fats. Their accumulation result in damage of micro and macro vascular damage that can lead to organ system failure.
There two type of diabetes.
Type1 Diabetes mellitus is an immune-mediated disorder, only 5 to 10 % diabetes patient’s falls under type1.
Type2 Diabetes results from environment influence superimposed on genetic predispotion. Type2 Diabetes mellitus is more prevalent than type1.
The Diabetes-Hearing Loss Connection
A study published in the journal of Otology and Neurotology explored the way that diabetes could affect hearing, and found that diabetes is related to hearing loss at all sound registers, suggesting that it can cause profound damage to the inner ear.
Your ear is a delicate structure — and one that you depend on every day. So when diabetes, especially with poorly controlled blood sugar, takes its toll on the small blood vessels throughout your body, you ears are damaged, too. And while other parts of your body can accommodate for damaged blood vessels by depending on alternative blood supplies, your ear lacks that option.
“There’s no redundancy in the blood supply to the inner ear,” explains Hearing loss researcher and otolaryngologist Yuri Agrawal, MD, assistant professor of otolaryngology at Johns Hopkins University in Baltimore. This means that once a blood vessel is damaged, there’s no back-up blood supply — and your hearing dulls accordingly. Along with losing your hearing, you will experience an increased risk of falling because your inner ear no only helps manage your hearing but also your sense of balance.
The most common hearing impairment seen is diabetes mellitus is progressive bilateral Sensori-neural Hearing loss of gradual onset, which mainly affects higher frequencies similar to age-related Hearing loss. The Hearing loss may also be unilateral, sudden with and without vestibular disorder.
Evidence shows that the endolymphatic sac vasculature plays an important role in pathogenesis of Sensori-neural Hearing Loss.
The main cause of Hearing loss in diabetes patients is poor blood flow (Vascular efficency) to the Cochlea. Uncontrolled diabetes may cause vasculopathy in the stria vascularis of the cochlea.
Researches have reported that, diffused thickening of the basilar membrane observed in vascular endothelium which is called diabetic microangiopathy. Microangiopathy is responsible for Hearing loss in Diabetic Individuals with the participation of smaller vessels in the inner ear that leads to hypoxia and causes Hearing loss.
Diabetic neuropathy and microangiopathy can cause high frequency hearing loss. Hearing loss in the high frequency region suggests that the cochlea may have been damaged by angiopathy in the stria vascularis, spiral ligament, and edema (fluid accumulation) in the stria vascularis leads to poor frequency and intensity coding. It also has been observed that hearing loss can be present at all frequencies from 250 Hz to 8,000 Hz in diabetic individuals.
Poor speech perception in noise among diabetic patients. The study suggests that the poor performance at the Brainstem, as well as the cortical level, results in decreased Quick SIN performance in individuals with diabetes mellitus. Also poor auditory brainstem response.
Otoacoustic emission (OAE) in diabetic individuals also shows earlier changes in micromechanical properties of outer hair cells and poor auditory evoked brainstem responses in diabetic population.
The occurrence of delayed wave latencies of auditory brainstem responses were 64%, 72%, and 84% at 2kHz, 4kHz and 6kHz respectively, involvement of Central neural axis. This study also suggests that ABRs carried out at higher frequency, like 6 kHz, can be for early detection of central involvement in individuals with diabetes.