Diabetes and Diet: Blood Sugar and Dementia

Diabetes increases the risk of Alzheimer’s disease and other dementias. But what about blood sugar levels that are elevated, but not high enough to be diabetes?

Researchers tracked 2,067 people aged 65 and older (most were in their 70s) in the Adult Changes in Thought (ACT) study for seven years.


Among participants who didn’t have diabetes, the higher their average fasting blood sugar over the previous five years, the higher their risk of dementia. For example, those who had an average fasting blood sugar of 115 mg/dL were 18 percent more likely to be diagnosed with dementia than those with a fasting blood sugar of 100 mg/dL.

Among participants with diabetes, those with an average fasting blood sugar of 190 mg/dL had a 40 percent higher risk of dementia than those with a fasting blood sugar of 160 mg/dL.

(A fasting blood sugar level is normal if it’s below 100 mg/dL. You have prediabetes if it’s 100 to 125 mg/dL and diabetes if it’s over 125 mg/dL.)

What to do: This study can’t prove that high blood sugar causes dementia, but it’s one more reason to keep blood sugar levels normal. The best strategy: lose excess weight and exercise. Even short bouts of brisk walking several times throughout the day can help. It’s also worth limiting foods that raise blood sugar levels rapidly, especially sugar-sweetened beverages.

Source: N. Engl. J. Med. 369: 540, 2013.


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