The Link Between Type 2 Diabetes and Dementia

People with diabetes are almost 60% more likely to develop dementia. Could Dementia be Type 3 Diabetes?

What is Dementia?

The National Institute on Aging defines dementia as a loss of cognitive functioning, such as thinking, remembering, and reasoning. This is not the typical misplacement of keys or forgetting why you walked into a room – this is cognitive dysfunction that interferes with the ability to perform daily activities.

Dementia is a progressive, neurodegenerative brain disease and the sixth-leading cause of death in the United States. Alzheimer’s Disease, the most common form of dementia, is caused by abnormal buildups of proteins in the brain called amyloid plaques and tau tangles. These protein build-ups cause changes in the brain, leading to common symptoms, including forgetting how to complete basic self-care tasks, personality changes, an inability to control emotions, and no longer recognizing friends and loved ones.

Though nearly 7 million people in the U.S. aged 65 years or older have dementia, it is not considered a normal part of aging. By 2060, the number of people with dementia is expected to double to 14 million.

There is no cure for dementia. Some medications have been shown to slow the progression of symptoms. The average life expectancy after diagnosis of dementia is 4 to 8 years.

Dementia is frustrating and frightening for the person suffering from it. It is also distressing and devastating for the loved ones caring for a person with dementia as they slowly watch their once vibrant loved one become a shell of themselves.

What is Type 2 Diabetes?

Type 2 diabetes (T2DM) is a prevalent type of diabetes, accounting for approximately 95% of all diabetes cases. It is a chronic condition characterized by elevated blood sugar levels resulting from insufficient insulin production or insulin resistance.

Insulin is a hormone made in the pancreas that helps move sugar out of your bloodstream and into your cells that need it for energy.

The symptoms are often very subtle and can be easily overlooked. They include increased frequency in urination, increased thirst, increased hunger despite consuming enough calories, changes in vision such as blurred vision, extreme fatigue, wounds that are slow to heal, and numbness, tingling, or pain in your hands or feet.

T2DM is a serious health condition that requires proper management and treatment to prevent complications and improve quality of life. More than 38 million people in the U.S. have T2DM, and nearly 98 million more have pre-diabetes. Uncontrolled T2DM is a risk factor for many serious health problems, such as:

• Heart disease

• Stroke

• Nerve damage

• Kidney disease

• Eye disease

• Sexual dysfunction

• Nonalcoholic fatty liver disease (NAFLD)

• Sleep apnea

• Depression

• Some forms of cancer

• Dementia

If caught early enough, T2DM may be managed with diet and exercise. As it progresses, T2DM management may require oral or injectable medications.

What is the Link between Diabetes and Dementia?

Research has shown that 25-36% of people with T2DM have cognitive impairments and progress to dementia more quickly than people without T2DM. This has led to the Type 3 Diabetes (T3DM) theory.

What is Type 3 Diabetes?

Studies have shown that insulin plays a vital role in the brain’s neurotransmitters, maintenance of energy, and memory capacity. Some researchers have proposed that Alzheimer’s Disease (AD), the most common form of dementia, is T3DM because of many common mechanisms noted between T2DM and AD. The International Journal of Molecular Science released a review article outlining these overlapping mechanisms, which include:

• Disrupted insulin signaling

• Insulin resistance

• Neuroinflammation

• Oxidative stress

• Mitochondrial dysfunction

• Metabolic syndrome

• Beta-amyloid, tau protein, and amylin plaques in the brain

What does diabetes and dementia research show?

Is dementia a form of diabetes? A December 2023 meta-analysis published in Frontiers of Neuroscience sought to answer this question.

The researchers reviewed MRI scans of patients with T2DM, patients with AD, and healthy control patients. The study concluded that while T2DM and AD have strong epidemiological correlations, they determined that they are two separate disease processes and could not endorse the concept of AD or other forms of dementia as Type 3 Diabetes.

The American Diabetes Association (ADA) and the medical community reject the term Type 3 Diabetes, and it is not an official medical diagnosis. The ADA does recognize insulin's effects on the brain as a critical factor in memory and other cognitive processes and T2DM’s role in predicting cognitive impairment and decline. Population-based studies have demonstrated an association between T2DM and:

• Global cognitive decline at twice the rate of those without T2DM

• General cognitive slowing

• Episodic memory decline

• Decreased executive function, including verbal fluency, working memory, processing speed, cognitive flexibility, and cognitive control

The Journal of American Medical Association released a prospective cohort study of 10,095 participants looking at the association between age at the onset of diabetes and the subsequent risk of dementia. The study concluded that earlier onset of T2DM correlated with a greater risk of developing dementia. The rate of dementia at age 70 in people without T2DM was 8.9 per 1,000 compared to:

• 10.0 per 1,000 people diagnosed with T2DM at age 65

• 13.0 per 1,000 people diagnosed with T2DM between ages 60 and 65

• 18.3 per 1,000 people diagnosed with T2DM before age 60

The link between diabetes and dementia extends to some common modifiable risk factors for both, such as:

• Obesity

• Sedentary lifestyle

• Poor diet

Additional risk factors for dementia include cigarette smoking, excessive alcohol use, high blood pressure, depression, and diabetes.

What Can You Do to Reduce Your Risk?

The best way to reduce your risk for diabetes and dementia is to address your modifiable risk factors – those factors that you have control over, such as:

• Maintain a healthy weight – Start with minor changes. Trade out sugary, empty-calorie drinks for water. Try the Diabetes Plate Method, which advises filling half your plate with non-starchy vegetables, one-quarter with lean proteins, and the final quarter with carbohydrates.

• Adopt an active lifestyle – Aim for at least 150 minutes of moderately intense weekly activity. Find activities you enjoy because you will be more likely to remain committed to something you look forward to.

• Reduce your intake of processed foods – Choose fresh fruits, vegetables, and nuts over processed foods. Pre-plan meals and snacks to help avoid the convenience of processed foods.

• Stop smoking – Enlist the help and support of loved ones to help quit smoking and try these helpful resources.

• Only consume alcohol in moderation – Alcohol is full of empty calories and often lowers our inhibitions to over-consume foods when we indulge.

• Maintain healthy blood pressure—Maintaining a healthy weight, being active, reducing processed food consumption, and quitting smoking will all help. However, monitoring your blood pressure to ensure a healthy reading is helpful. If your readings are elevated, generally over 120/80, you should speak with your provider about further ways to lower your blood pressure.

• Establish a relationship with a Primary Care Provider (PCP) – Routine health exams can help you monitor lab results that may indicate health risks, such as an elevated hemoglobin A1c, an average blood sugar over the past 90 days.

If you have a family history of T2DM or dementia, your PCP can provide further information about signs to watch for and lifestyle modifications to adopt. If you have already been diagnosed with T2DM, you and your PCP can work together to manage your disease and help stave off other diseases T2DM places you at risk, including dementia.

Conclusion

The research does not currently support the theory that dementia is Type 3 diabetes, though more research continues to explore this theory. However, there is significant evidence that diabetes and dementia share many common risk factors, and diabetes is a risk factor for dementia. Preventing your risk of diabetes could very well prevent your risk of dementia as well and lead to more years of quality life.

Where To Find More Information

The American Diabetes Association provides more information about T2DM, and the National Institute on Aging and the Alzheimer’s Association provide more information about dementia.