Dementia risk increased by higher blood sugar before diabetes

Dementia and its association with insulin dysregulation and diabetes has been described by a number of investigators but this bears repeating on the occasion of a paper just published in The New England Journal of Medicine. The authors determined to see if blood sugar elevated to a lesser degree than in diabetes is linked to dementia:

"Diabetes is a risk factor for dementia. It is unknown whether higher glucose levels increase the risk of dementia in people without diabetes."

They examined glucose and glycated hemoglobin (HgbA1c) levels in 2067 subjects without dementia and followed them for an average of 6.8 years (adjusting for a number of variables that could also contribute to dementia) and found a clear association:

"During a median follow-up of 6.8 years, dementia developed in 524 participants (74 with diabetes and 450 without). Among participants without diabetes, higher average glucose levels within the preceding 5 years were related to an increased risk of dementia; with a glucose level of 115 mg per deciliter (6.4 mmol per liter) as compared with 100 mg per deciliter (5.5 mmol per liter), the adjusted hazard ratio for dementia was 1.18.

With diabetes, of course, it was worse:

"Among participants with diabetes, higher average glucose levels were also related to an increased risk of dementia; with a glucose level of 190 mg per deciliter (10.5 mmol per liter) as compared with 160 mg per deciliter (8.9 mmol per liter), the adjusted hazard ratio was 1.40."

But insulin resistance and rising blood glucose levels do not have to evolve as far as type 2 diabetes to add to the risk for dementia as the authors conclude:

"Our results suggest that higher glucose levels may be a risk factor for dementia, even among persons without diabetes."