There’s a well-known relationship between diabetes and dementia, although the mechanisms behind the connection are not totally clear.

It may be that the chances of developing atherosclerosis or narrowing of the arteries are higher in those with diabetes, which could affect the brain’s blood vessels. It has also been suggested that the stress diabetes puts on the body could possibly lead to metabolic problems in the brain.

A new study finds that high blood sugar alone — even in people who don’t have diabetes — may also be linked to an increased risk for dementia.

Your body turns your food into glucose, so your blood sugar levels depend not only on what you eat but also on your individual metabolism: how your body handles your food.

The research team followed 2,000 people over a period of almost seven years. The team looked at current blood sugar levels, along with another measure of blood glucose known as glycated hemoglobin (HbA1c), which reflects blood sugar over the longer term. The researchers then analyzed how the two measures related to the risk of developing dementia.

There were some striking findings for people with and without diabetes. For people without diabetes but whose blood sugar was slightly high, at 115 mg/dl (normal is 70-100 mg/dl), the dementia risk was 18% higher, compared to non-diabetic people whose blood sugar was 100 mg/dl.

For people with diabetes, those who had blood sugar of 190 mg/dl had a 40% greater risk of developing dementia, compared to diabetics with glucose of 160 mg/dl.

“The most interesting finding,” author Paul K. Crane said in a statement, “was that every incrementally higher glucose level was associated with a higher risk of dementia in people who did not have diabetes. There was no threshold value for lower glucose values where risk leveled off.”

This prospect is somewhat sobering, and good reason to keep blood sugar in the normal range, with a healthy diet and regular exercise. The authors do caution that their study does not show cause-and-effect, but it does offer a strong correlation between the two variables. Future studies will be needed to answer the question of whether reducing blood sugar might directly reduce dementia risk.

Crane pointed out that cutting out sugar or carbs is not necessarily the only – or the best – way. “Your body turns your food into glucose, so your blood sugar levels depend not only on what you eat but also on your individual metabolism: how your body handles your food. ” So a better idea, he says, might be to add exercise into your daily routine, if you can, since this has been shown to affect not only blood sugar levels but is also linked to lower dementia risk.

The study was carried out by a team at the University of Washington School of Medicine and published in The New England Journal of Medicine.