For many years, doctors treated diabetes and dementia as two separate health problems. Diabetes was mainly seen as a disease that affects blood sugar and damages organs such as the heart, kidneys, and eyes.
Dementia was viewed as a disorder of memory and thinking that happens in the brain. Today, scientists are finding that these two conditions are much more closely connected than once believed.
Research from around the world is showing that problems with blood sugar can affect brain health, and changes in the brain may also influence how the body controls glucose. This growing body of evidence suggests that protecting metabolic health could be an important part of keeping the brain healthy as we age.
Diabetes is becoming increasingly common. Hundreds of millions of people around the world are living with the disease, and most have type 2 diabetes. In this condition, the body gradually becomes resistant to insulin.
Insulin is a hormone that allows glucose, a form of sugar, to move from the bloodstream into cells where it can be used for energy. When insulin stops working properly, sugar remains in the blood and slowly damages tissues throughout the body.
Dementia is also a major public health challenge. It is not a single disease but a group of conditions that affect memory, thinking, language, and daily functioning. Alzheimer’s disease is the most common form of dementia.
Because both diabetes and dementia become more common with age, many researchers have been trying to understand whether they share common biological pathways.
Studies now show that people with diabetes are about 60 percent more likely to develop dementia than those without diabetes. Researchers have also found that repeated episodes of low blood sugar are associated with a much higher risk of memory problems and cognitive decline.
One reason for this connection may be insulin resistance in the brain. Although the brain accounts for only a small percentage of body weight, it consumes around one-fifth of the body’s total energy. Brain cells depend heavily on glucose to perform their many functions, including storing memories, controlling movement, and processing information.
Scientists have discovered that in Alzheimer’s disease, brain cells often struggle to use glucose properly. They become less responsive to insulin and have difficulty producing enough energy. Because this problem resembles some aspects of type 2 diabetes, some researchers have informally described Alzheimer’s disease as “type 3 diabetes.”
The relationship appears to work in both directions. Studies have shown that people with Alzheimer’s disease often have higher fasting blood sugar levels, even when they do not have diabetes.
Research in animals has also found that Alzheimer’s-related changes in the brain can raise blood glucose levels. In addition, people who carry a gene called APOE4, which is one of the strongest known genetic risk factors for Alzheimer’s disease, often show reduced sensitivity to insulin.
Blood vessel damage provides another important connection. Diabetes can injure blood vessels throughout the body. Most people know that it can lead to complications involving the heart, kidneys, and eyes, but the brain is also highly vulnerable.
Persistently high blood sugar and large swings in glucose levels can damage the tiny blood vessels that nourish brain tissue. Reduced blood flow means less oxygen and fewer nutrients reach brain cells.
Diabetes may also weaken the blood-brain barrier, a protective system that normally keeps harmful substances out of the brain. When this barrier becomes damaged, inflammation can develop. Scientists increasingly believe that chronic inflammation is an important contributor to dementia.
The growing understanding of these links has led researchers to examine whether diabetes medications could also benefit the brain. Some of the findings have been encouraging.
Memantine, a medication now used to treat moderate to severe Alzheimer’s disease symptoms, was originally developed as a diabetes drug. Although it did not become a successful treatment for blood sugar control, researchers later discovered that it could improve certain aspects of brain function.
Metformin, the most widely prescribed medicine for type 2 diabetes, has also attracted attention. Studies suggest that it may lower inflammation in the brain. Some research indicates that people with diabetes who take metformin have a lower risk of developing dementia.
Newer medications may offer even greater promise. GLP-1 receptor agonists, including drugs such as Ozempic and Wegovy, lower blood sugar and promote weight loss.
Studies have found that people taking these medications may have a lower risk of dementia. Large clinical trials are now investigating whether these drugs can slow cognitive decline in people with early Alzheimer’s disease.
Researchers are also studying SGLT2 inhibitors, which reduce blood sugar by helping the body remove excess glucose through urine. Early evidence suggests that these drugs may lower inflammation in the brain and reduce the risk of Alzheimer’s disease and vascular dementia.
Scientists have even explored delivering insulin directly to the brain through nasal sprays. Small studies suggest that this approach may improve memory and possibly slow brain shrinkage, although larger studies are still needed.
After reviewing the available evidence, researchers increasingly believe that maintaining healthy blood sugar levels may be one of the keys to preserving brain health. Diabetes and dementia appear to share several biological pathways, including insulin resistance, inflammation, blood vessel injury, and problems with energy production in brain cells.
While many questions remain unanswered, these findings offer hope that better management of diabetes could eventually become an important strategy for preventing or delaying dementia. They also suggest that treatments originally developed for diabetes may one day play a significant role in protecting the aging brain.
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Source: The Conversation.
