What Is Type 3 Diabetes?

Older adults with Alzheimer's Disease

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In 1906, German psychiatrist and neuropathologist Alois Alzheimer examined the brain of a woman who died from abnormal psychopathological conditions. He researched the neurocognitive changes in her brain tissue and, before she died, identified her symptoms, such as memory loss, language problems, and abnormal behavior. Alzheimer highlighted “many abnormal clumps (i.e., amyloid plaques) and tangled fiber bundles (i.e., neurofibrillary, or tau, tangles)" (National Institute on Aging [NIA], 2023, para. 4). The unusual neuropsychiatric condition was named after him: Alzheimer's disease.

Alzheimer’s disease (AD) is a progressive condition that significantly impacts brain cognition, memory, and other essential high-executive function capabilities over time. Due to eventual cognitive impairment, the disease affects how a person completes simple tasks and daily responsibilities and alters their behaviors and emotions. Individuals diagnosed with AD experience the degeneration and eventual death of brain cells and their connections within the neural system. The disease is the most common cause of dementia, accounting for up to 80 percent of the cases, with approximately 14 million people projected to be diagnosed by 2060 (Centers for Disease and Prevention, 2024).

There are two types of AD: early and late-onset. Early-onset symptoms appear before one reaches 60; late-onset, the most common form, is diagnosed in individuals 60 and older. Because AD diagnoses tend to double, particularly by age 65, it is essential to be cognizant of the symptoms, as AD can occur to anyone and is predicated on various factors.

• Anger
• Behavioral changes
• Confusion
• Difficulty completing daily tasks
• Trouble with understanding and using written and spoken language
• Reduced judgement
• Forgetfulness
• Impaired reasoning or judgment
• Irritability
• Mood and personality changes
• Visual and spatial concerns
• Withdrawal

Age-related changes and environmental, genetic, and lifestyle factors are common causes of AD. Protein buildup in brain cells (e.g., amyloid and tau) forms plaques and tangles—the plaques and tangles cause brain dysfunction, which damages those cells and eventually causes cell death. According to the National Institutes of Health (NIH) (2023), AD is the seventh leading cause of death in the United States and has a significant causal relationship between dementia and gero-cognitive conditions in older adults.

Regarding dementia, the condition can vary and is dependent upon neurocognitive changes over time. Besides AD, there are other dementia types, including frontotemporal, Lewy body, mixed (i.e., diagnosed with two or more dementia types), and vascular. There is no cure for AD; however, there are medicinal therapies and treatments that can prevent progressive decline and may temporarily improve symptoms. Nonetheless, advanced stages of AD result in significant brain dysfunction, leading to other medical conditions, and such medical complications can be fatal.

The Facts About Diabetes

Glucose meter

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Diabetes mellitus is an endocrine or metabolic condition where the body has difficulty processing glucose. Most importantly, the body struggles to convert sugar into energy; therefore, excessive glucose levels remain within the bloodstream due to a lack of insulin production or inappropriate response to insulin levels.

Sapra and Bhandari (2023) purport that there are various forms of diabetes: Type 1 diabetes (T1D), type 2 diabetes (T2D), maturity-onset diabetes of the young (MODY), gestational, neonatal, and steroid-induced. T1D is a hereditary and chronic condition in which the body’s endocrine system, particularly the pancreas, does not produce sufficient insulin, resulting in high glucose levels.

Formally known as “juvenile diabetes,” T1D cannot be cured. T2D is also a chronic condition where the body has difficulty producing insulin; however, this type is mainly linked to health and proper dieting. Poor health and eating habits can lead to insulin resistance and high glucose levels. MODY is a monogenic diabetes form due to autosomal dominant genes interrupting insulin production. It is a rare genetic disease, and if a parent has the gene mutation, its offspring has a 50 percent possibility of inheriting it. Currently, there is no cure; however, it can be managed with sulfonylurea treatment (Hoffman et al., 2023). Gestational diabetes develops when the body becomes insulin-resistant due to specific hormones produced during pregnancy. Though it can be reversed with proper dieting, exercise, and insulin, mothers are still at risk of developing T2D following delivery.

Neonatal diabetes (NDM) occurs in infants who cannot produce insulin. Another form of monogenic diabetes, NDM, is developed by a single gene mutation that interrupts pancreatic beta cell function and forms in the baby’s first six months of life. More than half of the infants diagnosed with NDM have it permanently, while others may experience it temporarily (National Institute of Diabetes and Digestive and Kidney Diseases, 2023). Finally, steroid-induced diabetes is highly likely for those at risk for T2D due to heightened glucose levels linked to glucocorticoids (steroid hormones produced within the adrenal gland and are essential for glucose, fat, and protein metabolism).

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Why Is Alzheimer's Disease Rumored as Type 3 Diabetes?

Glucose meter, needle for insulin, and medication

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T3D is not officially recognized by organizations such as the American Diabetic Association, the American Medical Association, or the American Psychiatric Association. However, some experts have coined AD as type 3 diabetes due to pathological implications that address a substantial decrease in glucose levels and how that affects brain cognition and memory. Based on insulin resistance and insulin theories, there may be a growth dysfunction linked to AD, which leads to cognitive and memory decline. Learning more about their relationship is essential as the term T3D emerges within the neuropsychiatric and medical communities.

Another term has been publicized in evidentiary and experiential-based research, known as type 3c diabetes mellitus or T3cDM, pancreatogenesis diabetes. This form of diabetes occurs when endocrinologic dysfunction affects the pancreas, such as damage to the exocrine glands, which harms the endocrine glands. This condition is distinctive and not to be confused with T3D.

Nonetheless, limited evidence-based research purports that the term T3D is used because insulin resistance or intolerance impacts the brain and can lead to dementia. For example, one of the earliest research articles used human and animal studies to explain how diabetes affects the brain, causing AD. De la Monte and Wands (2008) reported that AD can cause inflammation and oxidative stress, which is significant to cognitive performance due to insulin dysfunction, strengthening the argument that the condition is caused by diabetes.

A patient with Alzheimer's Disease and his family

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However, Mittal et al. (2016) suggested that a specific enzyme (i.e., insulin-degrading enzyme) is a significant factor in delineating diabetes, particularly T2D to T3D, as metabolic pathways are changed due to beta-cell development regulation dysregulation, leading to amyloid-beta dilapidation. A more recent study expressed the relationship between prevalent risk factors of T2D, which includes “diets high in calories, sugar, and fat, diets low in fiber, low socioeconomic status, stress, race and ethnicity, lack of physical activity, genetics, family history, and birth weight” (Nguyen et al., 2020). Most importantly, the experts emphasized that hypertension and fat are critical factors in AD.

As information about T3D continues to increase, additional research is needed to understand the neuropsychiatric and medical implications of diabetes and AD.