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Hearing loss in diabetes is a form of hearing impairment resulting from type 2 diabetes mellitus. [1] Type 2 diabetes mellitus (T2DM) is associated with various microvascular and macrovascular complications. Microvascular complications include diabetic retinopathy, neuropathy, and nephropathy, while macrovascular complications involve cerebrovascular disease, peripheral vascular disease, and coronary heart disease. [2] T2DM also affects other systems such as the hepatic and digestive systems, musculoskeletal system, and can impact mental health and cognitive functioning. These complications significantly contribute to the disease's overall burden. The rising prevalence of T2DM is expected to increase the number of individuals experiencing these complications. Additionally, similar pathophysiological mechanisms may lead to damage in the neural system or vasculature of the inner ear, resulting in hearing impairment. Numerous population-based studies have demonstrated a significant association between T2DM and hearing loss, particularly sensorineural hearing loss, [3] [4] which tends to worsen as T2DM progresses.
The Centre for Disease Control and Prevention (CDC) recommends a baseline hearing evaluation upon diagnosis of diabetes and a complete audiological evaluation every two years following that. The American Speech-Language-Hearing Association and the World Health Organization's Guidelines on Integrated Care for Older People recommend screening and provision of amplification among older adults.
Among these complications, sensorineural hearing loss is significant, with its severity correlating with T2DM progression. Hearing loss impacts quality of life, causing economic and emotional strain. It is an independent risk factor for dementia, cognitive decline, social withdrawal, anxiety, depression, and physical decline, especially in older adults. Both T2DM and hearing loss independently increase dementia risk. Among patients with diabetes, age, nephropathy, and neuropathy [5] were associated with hearing loss.[ citation needed ]
Identifying high-risk individuals for complications like hearing loss can enable early diagnosis and intervention. This article explores the association between hearing loss and diabetes and discusses screening guidelines and tools for diabetic patients.
Hearing impairment in type 2 diabetes mellitus (T2DM) is thought to be caused by several pathophysiological mechanisms, including microangiopathy, neuropathy, and mitochondrial damage. Microangiopathy in diabetes results from glycoprotein accumulation and endothelial damage, affecting highly microvascular structures like the cochlea. Studies have linked factors such as HbA1c levels, uncontrolled blood sugar, diabetic neuropathy, retinopathy and nephropathy to an increased risk of hearing loss in diabetic patients. The stria vascularis in the cochlea, crucial for fluid homeostasis and sound transduction, can be damaged by microangiopathy. This damage includes thickened capillary walls and lumen narrowing, as well as degeneration of the stria vascularis observed in patients with T2DM. [6] [7] [8]
Outer hair cells, essential for sound amplification, can be damaged in diabetes, leading to hearing impairment. Thickening of the capillary basement membrane and a reduction in ganglion cells within the spiral ganglion have been noted, impacting the neural transmission pathways. Oxidative stress and increased free radical production in diabetics contribute to neural damage and delayed neural conduction, affecting hearing. [9]
Hyperglycemia can lead to chronic cochlear damage or impaired endolymph homeostasis, affecting pure-tone audiometry (PTA) thresholds. Reactive oxygen species (ROS) like nitric oxide are higher in diabetics with hearing loss, indicating oxidative stress's role in hearing impairment. Additional factors such as dyslipidemia, insulin resistance, and hypertension can further negatively impact hearing in individuals with diabetes. [10] [11]
Recent studies highlight the lower odds of hearing aid use in older adults with diabetes or hypertension, emphasizing the need to identify and address hearing impairment in this population. Even subclinical hearing loss can lead to cognitive impairment and depressive symptoms, with a minimal increase in the pure-tone audiometry (PTA) hearing threshold linked to higher risks of social isolation and cognitive decline. Timely diagnosis and hearing aid use can significantly improve quality of life, reduce depression, and mitigate cognitive decline. [12] [13]
Despite its prevalence, hearing loss is under-diagnosed and under-treated, particularly in older adults who may underestimate their impairment. Early diagnosis and intervention are crucial for better compliance and treatment outcomes in diabetic patients. Up to 75% of adults who could benefit from hearing aids do not use them, despite evidence showing that hearing aid users experience less depression and social isolation, better cognitive function and improved relationships. [14]
The CDC recommends baseline hearing evaluations upon diabetes diagnosis, followed by comprehensive audiological evaluations at least every two years, with more frequent evaluations for high-risk patients. The American Speech-Language-Hearing Association (ASHA) suggests screenings once per decade for adults, increasing to once every three years after age 50. The World Health Organization also recommends hearing loss screening and amplification for older adults. However, the American Diabetes Association does not currently recommend routine hearing screening for diabetic patients.
There is debate about universal hearing screening for adults. The US Preventive Services Task Force and the American Academy of Family Physicians find insufficient evidence to recommend routine screening for asymptomatic adults over 50. The UK National Screening Committee does not support a national screening program for this age group. Nonetheless, some experts suggest screening those with perceived hearing loss or known risk factors.
Screening tools for hearing loss in diabetic patients include clinical tests like the whispered voice or finger rub tests, single-question screenings, the Hearing Handicap Inventory for the Elderly-Screening (HHIE-S), and hand-held audiometers. Single-question screening has shown reasonable accuracy, and the HHIE-S has been validated with high sensitivity and specificity for older adults. Smartphone apps for hearing tests, such as uHear and hearWHO, also show promise with high accuracy. [15] [16]
Diabetic retinopathy, is a medical condition in which damage occurs to the retina due to diabetes. It is a leading cause of blindness in developed countries.
Hyperglycemia or Hyperglycaemia is a condition in which an excessive amount of glucose (glucotoxicity) circulates in the blood plasma. This is generally a blood sugar level higher than 11.1 mmol/L (200 mg/dL), but symptoms may not start to become noticeable until even higher values such as 13.9–16.7 mmol/L (~250–300 mg/dL). A subject with a consistent fasting blood glucose range between ~5.6 and ~7 mmol/L is considered slightly hyperglycemic, and above 7 mmol/L is generally held to have diabetes. For diabetics, glucose levels that are considered to be too hyperglycemic can vary from person to person, mainly due to the person's renal threshold of glucose and overall glucose tolerance. On average, however, chronic levels above 10–12 mmol/L (180–216 mg/dL) can produce noticeable organ damage over time.
Type 2 diabetes (T2D), formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, fatigue and unexplained weight loss. Other symptoms include increased hunger, having a sensation of pins and needles, and sores (wounds) that heal slowly. Symptoms often develop slowly. Long-term complications from high blood sugar include heart disease, stroke, diabetic retinopathy, which can result in blindness, kidney failure, and poor blood flow in the lower-limbs, which may lead to amputations. The sudden onset of hyperosmolar hyperglycemic state may occur; however, ketoacidosis is uncommon.
Microangiopathy is a disease of the microvessels, small blood vessels in the microcirculation. It can be contrasted to macroangiopathies such as atherosclerosis, where large and medium-sized arteries are primarily affected.
Diabetic neuropathy includes various types of nerve damage associated with diabetes mellitus. The most common form, diabetic peripheral neuropathy, affects 30% of all diabetic patients. Symptoms depend on the site of nerve damage and can include motor changes such as weakness; sensory symptoms such as numbness, tingling, or pain; or autonomic changes such as urinary symptoms. These changes are thought to result from a microvascular injury involving small blood vessels that supply nerves. Relatively common conditions which may be associated with diabetic neuropathy include distal symmetric polyneuropathy; third, fourth, or sixth cranial nerve palsy; mononeuropathy; mononeuropathy multiplex; diabetic amyotrophy; and autonomic neuropathy.
Wolfram syndrome, also called DIDMOAD, is a rare autosomal-recessive genetic disorder that causes childhood-onset diabetes mellitus, optic atrophy, and deafness as well as various other possible disorders including neurodegeneration. Symptoms can start to appear as early as childhood to adult years. There is a 25% recurrence risk in children.
Glycated hemoglobin, glycohemoglobin, glycosylated hemoglobin is a form of hemoglobin (Hb) that is chemically linked to a sugar. Several types of glycated hemoglobin measures exist, of which HbA1c, or simply A1c, is a standard single test. Most monosaccharides, including glucose, galactose, and fructose, spontaneously bond with hemoglobin when present in the bloodstream. However, glucose is only 21% as likely to do so as galactose and 13% as likely to do so as fructose, which may explain why glucose is used as the primary metabolic fuel in humans.
A complication in medicine, or medical complication, is an unfavorable result of a disease, health condition, or treatment. Complications may adversely affect the prognosis, or outcome, of a disease. Complications generally involve a worsening in the severity of the disease or the development of new signs, symptoms, or pathological changes that may become widespread throughout the body and affect other organ systems. Thus, complications may lead to the development of new diseases resulting from previously existing diseases. Complications may also arise as a result of various treatments.
Diabetic nephropathy, also known as diabetic kidney disease, is the chronic loss of kidney function occurring in those with diabetes mellitus. Diabetic nephropathy is the leading causes of chronic kidney disease (CKD) and end-stage renal disease (ESRD) globally. The triad of protein leaking into the urine, rising blood pressure with hypertension and then falling renal function is common to many forms of CKD. Protein loss in the urine due to damage of the glomeruli may become massive, and cause a low serum albumin with resulting generalized body swelling (edema) so called nephrotic syndrome. Likewise, the estimated glomerular filtration rate (eGFR) may progressively fall from a normal of over 90 ml/min/1.73m2 to less than 15, at which point the patient is said to have end-stage renal disease. It usually is slowly progressive over years.
Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that originates when cells that make insulin are destroyed by the immune system. Insulin is a hormone required for the cells to use blood sugar for energy and it helps regulate glucose levels in the bloodstream. It results in high blood sugar levels in the body prior to treatment. The common symptoms of this elevated blood sugar are frequent urination, increased thirst, increased hunger, weight loss, and other serious complications. Additional symptoms may include blurry vision, tiredness, and slow wound healing. Symptoms typically develop over a short period of time, often a matter of weeks if not months.
The term diabetes includes several different metabolic disorders that all, if left untreated, result in abnormally high concentrations of a sugar called glucose in the blood. Diabetes mellitus type 1 results when the pancreas no longer produces significant amounts of the hormone insulin, usually owing to the autoimmune destruction of the insulin-producing beta cells of the pancreas. Diabetes mellitus type 2, in contrast, is now thought to result from autoimmune attacks on the pancreas and/or insulin resistance. The pancreas of a person with type 2 diabetes may be producing normal or even abnormally large amounts of insulin. Other forms of diabetes mellitus, such as the various forms of maturity-onset diabetes of the young, may represent some combination of insufficient insulin production and insulin resistance. Some degree of insulin resistance may also be present in a person with type 1 diabetes.
Diabetic angiopathy is a form of angiopathy associated with diabetic complications. While not exclusive, the two most common forms are diabetic retinopathy and diabetic nephropathy, whose pathophysiologies are largely identical. Other forms of diabetic angiopathy include diabetic neuropathy and diabetic cardiomyopathy.
Proximal diabetic neuropathy, also known as diabetic amyotrophy, is a complication of diabetes mellitus that affects the nerves that supply the thighs, hips, buttocks and/or lower legs. Proximal diabetic neuropathy is a type of diabetic neuropathy characterized by muscle wasting, weakness, pain, or changes in sensation/numbness of the leg. It is caused by damage to the nerves of the lumbosacral plexus.
Dilated fundus examination (DFE) is a diagnostic procedure that uses mydriatic eye drops to dilate or enlarge the pupil in order to obtain a better view of the fundus of the eye. Once the pupil is dilated, examiners use ophthalmoscopy to view the eye's interior, which makes it easier to assess the retina, optic nerve head, blood vessels, and other important features. DFE has been found to be a more effective method for evaluating eye health when compared to non-dilated examination, and is the best method of evaluating structures behind the iris. It is frequently performed by ophthalmologists and optometrists as part of an eye examination.
Prediabetes is a component of metabolic syndrome and is characterized by elevated blood sugar levels that fall below the threshold to diagnose diabetes mellitus. It usually does not cause symptoms but people with prediabetes often have obesity, dyslipidemia with high triglycerides and/or low HDL cholesterol, and hypertension. It is also associated with increased risk for cardiovascular disease (CVD). Prediabetes is more accurately considered an early stage of diabetes as health complications associated with type 2 diabetes often occur before the diagnosis of diabetes.
Diabetic cardiomyopathy is a disorder of the heart muscle in people with diabetes. It can lead to inability of the heart to circulate blood through the body effectively, a state known as heart failure(HF), with accumulation of fluid in the lungs or legs. Most heart failure in people with diabetes results from coronary artery disease, and diabetic cardiomyopathy is only said to exist if there is no coronary artery disease to explain the heart muscle disorder.
Complications of diabetes are secondary diseases that are a result of elevated blood glucose levels that occur in diabetic patients. These complications can be divided into two types: acute and chronic. Acute complications are complications that develop rapidly and can be exemplified as diabetic ketoacidosis (DKA), hyperglycemic hyperosmolar state (HHS), lactic acidosis (LA), and hypoglycemia. Chronic complications develop over time and are generally classified in two categories: microvascular and macrovascular. Microvascular complications include neuropathy, nephropathy, and retinopathy; while cardiovascular disease, stroke, and peripheral vascular disease are included in the macrovascular complications.
Diabetes mellitus, often known simply as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough insulin, or the cells of the body becoming unresponsive to the hormone's effects. Classic symptoms include thirst, polyuria, weight loss, and blurred vision. If left untreated, the disease can lead to various health complications, including disorders of the cardiovascular system, eye, kidney, and nerves. Diabetes accounts for approximately 4.2 million deaths every year, with an estimated 1.5 million caused by either untreated or poorly treated diabetes.
Type 3c diabetes is diabetes that comes secondary to pancreatic diseases, involving the exocrine and digestive functions of the pancreas. It also occurs following surgical removal of the pancreas.
Diabetic papillopathy is an ocular complication of diabetes mellitus characterized by optic disc swelling and edema of optic nerve head. The condition may affect both type 1 and type 2 diabetic patients.