Harvard Health Letter

High blood sugar linked to brain shrinkage

What this means for preventing cognitive decline

If your blood sugar is on the high end of the normal range, diabetes may not be your only risk. A recent study in Neurology suggests you're also at risk of brain shrinkage in areas associated with memory and thinking. "I do think that this is a legitimate association. However, we don't know if blood sugar causes it," says Dr. Gad Marshall, a neurologist at Harvard-affiliated Brigham and Women's Hospital.

A normal fasting blood sugar level is 70 to 100 milligrams per deciliter (mg/dL). Fasting is defined as at least six hours without eating or drinking anything with calories. A fasting level of 100 to 125 mg/dL indicates you have "prediabetes" and are at increased risk for developing diabetes. A fasting level of 126 mg/dL and higher signifies that you probably have diabetes.

Past research has already shown a link between type 2 diabetes and brain shrinkage. The new study finds that even people with fasting blood sugar levels at the high end of normal are more likely to have shrinkage in the brain.

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