Scientists are increasingly discovering that diabetes and dementia are closely connected. For many years, doctors thought of diabetes mainly as a disease that affects blood sugar, the heart, kidneys, and eyes.
Dementia, on the other hand, was seen as a completely separate brain disorder. However, new studies are showing that the two conditions influence each other in many surprising ways.
Diabetes is a condition in which the body has trouble controlling blood sugar levels. Type 2 diabetes, the most common form, usually develops because the body becomes resistant to insulin.
Insulin is a hormone that helps move sugar from the blood into cells, where it is used for energy. When insulin does not work properly, sugar remains in the bloodstream and can damage organs over time.
Dementia is a general term for diseases that cause memory loss, problems with thinking, and changes in behavior. Alzheimer’s disease is the most common form of dementia. Around the world, the number of people with both diabetes and dementia is rising rapidly as populations age.
Research shows that people with diabetes are about 60 percent more likely to develop dementia than people without diabetes. Episodes of very low blood sugar may also be harmful. Studies suggest that frequent low blood sugar events are linked to a roughly 50 percent higher risk of cognitive decline.
Scientists have found that insulin resistance does not affect only the muscles and liver. It also affects the brain. The brain makes up only about two percent of body weight, yet it uses around twenty percent of the body’s energy. Brain cells need a steady supply of glucose to function properly.
In Alzheimer’s disease, brain cells seem to lose some of their ability to use glucose efficiently. Because this process resembles some features of diabetes, some researchers informally call Alzheimer’s disease “type 3 diabetes.”
The relationship appears to go in both directions. Studies show that people with Alzheimer’s disease often have higher fasting blood sugar levels, even if they have never been diagnosed with diabetes.
Animal studies have also found that Alzheimer’s-like changes in the brain can increase blood sugar levels. In addition, a genetic variation called APOE4, which is one of the strongest genetic risk factors for Alzheimer’s disease, can reduce insulin sensitivity.
Another important link involves blood vessels. Diabetes can damage blood vessels throughout the body, causing problems in the eyes, kidneys, and heart. The brain is also vulnerable. High blood sugar and large swings in blood sugar levels can injure small blood vessels in the brain.
This can reduce blood flow and decrease the amount of oxygen reaching brain tissue. Diabetes may also weaken the brain’s protective barrier, allowing harmful substances to enter and trigger inflammation. Both poor blood flow and inflammation are strongly linked to dementia.
Interestingly, some medications developed for diabetes are showing promise for brain health. Memantine, a medicine used to treat moderate to severe Alzheimer’s disease symptoms, was originally created as a diabetes drug. Although it did not work well for controlling blood sugar, scientists later discovered that it could benefit brain function.
Metformin, the world’s most commonly used diabetes medicine, may also help protect the brain. The drug can enter the brain and may reduce inflammation. Some studies suggest that people with diabetes who take metformin are less likely to develop dementia. Researchers are even testing the medication in people who do not have diabetes.
Newer medications have also attracted attention. GLP-1 receptor agonists, including medicines such as Ozempic and Wegovy, lower blood sugar and help people lose weight. Studies have found that people with diabetes who use these medications appear to have a lower risk of dementia.
In some studies, they performed even better than metformin in reducing dementia risk. Large clinical trials are now investigating whether these drugs can help people with mild cognitive impairment or early Alzheimer’s disease.
Scientists have also tested insulin sprays that are delivered through the nose. This method allows insulin to reach the brain directly while minimizing effects on blood sugar. Early studies suggest that these sprays may improve memory or reduce brain shrinkage, although more research is needed to confirm their safety and effectiveness.
Another class of medications called SGLT2 inhibitors may also reduce dementia risk. These drugs lower blood sugar by helping the body remove excess sugar through urine. Early evidence suggests they may reduce inflammation in the brain and lower the risk of Alzheimer’s disease and vascular dementia.
After reviewing all of these findings, one message is becoming increasingly clear. Diabetes and dementia are deeply connected through problems involving blood sugar, insulin resistance, blood vessels, and inflammation. The evidence suggests that managing diabetes may help protect not only the heart and kidneys but also the brain.
At the same time, many important questions remain unanswered. Scientists still do not know whether diabetes medications can reduce dementia risk in people who do not have diabetes. More long-term studies are needed.
However, the growing research provides hope that treatments developed for diabetes may eventually become valuable tools for preserving brain health and reducing the burden of dementia as people age.
If you care about dementia, please read studies about dietary strategies to ward off dementia, and how omega-3 fatty acids fuel your mind.
For more health information, please see recent studies about Choline deficiency linked to Alzheimer’s disease, and what to eat (and avoid) for dementia prevention.
Source: The Conversation.
