# Does High Blood Sugar Worsen Dementia?
Your brain depends on glucose for energy, but when blood sugar levels stay too high for extended periods, it can damage the very structures that keep your mind sharp. Research shows a clear connection between poor blood sugar control and cognitive decline, suggesting that managing glucose levels may be one way to protect your brain health as you age.
People with diabetes face a significantly higher risk of developing dementia compared to those without the condition. Studies indicate that individuals with diabetes have about a 56 to 73 percent increased risk of developing Alzheimer’s disease and other forms of dementia. Even more concerning, this pattern holds true across different types of dementia, not just Alzheimer’s disease alone.
The damage happens through several pathways. When blood sugar remains chronically high, it can harm the small blood vessels that feed oxygen and nutrients to memory centers in the brain. This vascular damage reduces the delivery of these essential resources to the hippocampus and other regions responsible for memory and cognition. Over time, this reduced blood flow accelerates cognitive decline and increases the likelihood of memory loss.
Beyond blood vessel damage, high blood sugar disrupts how brain cells use energy. The brain normally relies on insulin to help neurons absorb and utilize glucose efficiently. When insulin signaling breaks down in the brain, even in people without full-blown diabetes, neurons struggle to get the energy they need to function properly. This energy shortage triggers inflammation within brain tissue and allows harmful proteins like amyloid-beta and tau to accumulate more easily. These protein buildups are hallmarks of Alzheimer’s disease.
Interestingly, brain insulin resistance can occur independently of diabetes. Research has shown that people with Alzheimer’s disease often have reduced insulin sensitivity in the brain, particularly in the hippocampus, even when their blood sugar levels appear normal. This brain-specific insulin resistance means that cells cannot use glucose efficiently, leading to energy deficits, weaker connections between neurons, and difficulty forming new memories.
The relationship between blood sugar and memory appears to follow a pattern. A large study conducted in Hong Kong found that adults had the lowest dementia risk when their long-term blood sugar control, measured by A1C levels, averaged in a moderate range of roughly 6.5 to 7.5 percent. Risk increased when A1C ran higher, but interestingly, dementia probability also crept up when average A1C dipped too low. This suggests that steady, moderate control offers the best protection for brain health, while both extremes pose risks.
Even people without diabetes should pay attention to their blood sugar levels. Research from Germany found that higher blood sugar levels, even within normal ranges and below diabetes thresholds, were associated with lower memory performance and structural changes in learning-relevant brain areas. Within normal A1C ranges, an increase of about 7 units on the blood test was tied to participants remembering approximately two fewer words after a 30-minute delay. Additionally, people with higher blood sugar levels showed smaller hippocampus volumes on brain imaging, suggesting that the brain’s memory center actually shrinks with chronically elevated glucose.
Some researchers have begun referring to Alzheimer’s disease as a form of “brain diabetes” because of these striking similarities in how insulin resistance damages the brain. The term “type 3 diabetes” has emerged in scientific literature to describe this condition where insulin resistance occurs specifically in the brain, impairing glucose uptake and contributing to neurodegeneration.
The good news is that managing blood sugar effectively may help reduce cognitive decline. Early and effective diabetes management has potential in reducing overall cognitive decline. Studies show that certain diabetes medications, including GLP-1 medicines and SGLT2 inhibitors, are associated with lower rates of Alzheimer’s and vascular dementia compared with other diabetes treatments. Movement also helps, as regular physical activity improves insulin sensitivity and blood flow to the brain. Even modest amounts of exercise, such as 20 to 30 minutes of brisk walking or water exercise most days, can make a difference.
Despite the strong correlation between diabetes and dementia, experts note a significant gap in clinical practice. Currently, there are no formal guidelines recommending routine Alzheimer’s screening in people with diabetes. However, many experts recommend that people with diabetes, particularly those with poor glycemic control, should have periodic cognitive assessments as part of their regular clinical care to monitor brain health.
Sources
https://www.charterresearch.com/news/diabetes-may-affect-your-memory/
https://www.consultant360.com/story/higher-blood-sugar-tied-memory-problems-study
https://nuffieldclinic.com/could-your-blood-sugar-be-affecting-how-you-think-remember-and-decide/