Seniors without diabetes but with higher than average blood sugar levels have an 18% increased risk for dementia, a new study shows.

In people with diabetes, the dementia risk was 40% higher for people with an average glucose level of 190 mg/dL, when compared to an average of 160 mg/dL, the study found.

Researchers tested more than 2,000 seniors. After seven years, they retested the older adults and found that slightly more than 500 had developed dementia. Almost all had higher average glucose levels, which correlated with an increased risk for dementia.