Elevated Blood Sugar Levels Linked to Dementia and Alzheimer’s Disease
Over the past decade, more and more studies have linked blood sugar (glucose) levels to problems with memory – up to and including dementia and Alzheimer’s disease – especially for people with diabetes.
A new study, based on a clinical trial at Charite University of Medicine, Berlin, Germany, indicates that elevated blood glucose levels, even for people without diabetes, can affect memory.
To repeat: even people with blood sugar levels below diabetes or pre-diabetes levels may have a risk of memory problems. This result, if verified and further described, increases the concern for the diet of people in most of the developed world – where foods such as fats and carbohydrates produce elevated blood sugar levels in a very large proportion of the population (about 60% in the U.S.).
Blood Glucose Levels and Memory Test Results of Clinical Trial
For the clinical trial in Berlin, 141 people between the ages of 50 and 80 years old were asked to fast for at least 10-12 hours. None of these people had diabetes or a history of memory problems. The researchers also excluded heavy drinkers and obese people.
After the fasting period, the researchers took a blood sample, which was used for the Glycosylated Hemoglobin A1C test that measures average blood glucose levels for the previous 90 days. Participants also had an MRI image taken of their brain.
To test their memory, each participant memorized a list of 15 unrelated words. After certain periods of time, they were asked to repeat the list of words.
How many words they remembered was correlated to the score of the GHA1C test, where 39 or less is considered normal and anything above 47.5 is considered diabetic. The researchers found that even as small an increase as 7 units above normal (e.g. around 45-46 on the GHA1C test) reduced the memory by an average of two words after 30 minutes.
Perhaps more disturbingly, the MRI tests revealed that people with higher blood glucose levels had a smaller hippocampus, the area of the brain most associated with memory. What this study may indicate is that sensitivity to blood sugar level may be greater than previously thought.
Interpreting the Clinical Trial Results: Are Blood Sugar Levels Responsible for Memory Loss?
Interpreting this study is not easy. On the surface, it sounds like we need to consider blood sugar level as a rather sensitive measurement of health – one with ramifications throughout the body, including the brain.
However, this was a first clinical trial of its type and the results, while unsettling, are by no means definitive. There are many questions not addressed in the trial, such as age related memory factors, general physical condition, environmental factors, or memory skills other than the one tested.
The researchers involved with the study clearly point out that the correlation between high(er) blood sugar levels and memory loss does not prove that this is a cause of the memory loss. While there are biochemical explanations for the connection (based on neuron chemistry), no one has yet been able to pinpoint and prove a causal link.
However, as this and numerous other observational studies highlight, high levels of blood sugar have a bad effect on many organs and processes of the body – the nervous system and brain included.
As is usually the case, more research is needed to sharpen the description of how much blood sugar affects what in which people. It would also be very helpful to pinpoint how blood sugar biochemically causes problems.
The take-home of the story is that the near epidemic of diabetes and the negative health effects of too much sugar in the blood, which is linked to high fat and carbohydrate-filled diets, need to have a higher level of emphasis by doctors and patients. It’s too important and too encompassing a problem to push it somewhere into the “well, it’s good for you to watch your diet” category of attention.