From UW Medicine Online News:
A joint Group Health–University of Washington study published in the New England Journal of Medicine has found that higher blood sugar levels are associated with higher dementia risk, even among people who do not have diabetes.
Blood sugar levels averaged over a five-year period were associated with rising risks for developing dementia, in this report of more than 2,000 Group Health patients age 65 and older in the Adult Changes in Thought (ACT) study. The study follows adults age 65 and older to identify risk factors for cognitive decline with aging and related conditions, such as Alzheimer's disease. Men and women with no cognitive impairment were randomly selected and invited to participate.
For example, in people without diabetes, risk for dementia was 18 percent higher for people with an average glucose level of 115 milligrams per deciliter compared to those with an average glucose level of 100 mg/dl. And in people with diabetes, whose blood sugar levels are generally higher, dementia risk was 40 percent higher for people with an average glucose level of 190 mg/dl compared to those with an average glucose level of 160 mg/dl.
“The most interesting finding was that every incrementally higher glucose level was associated with a higher risk of dementia in people who did not have diabetes,” said first author Paul K. Crane, UW associate professor of medicine, and affiliate investigator at Group Health Research Institute. “There was no threshold value for lower glucose values where risk leveled off.”
“One major strength of this research is that it is based on the ACT study, a longitudinal cohort study, where we follow people for many years as they lead their lives,” said senior author Eric B. Larson, a senior investigator at Group Health Research Institute who also has appointments at the UW Schools of Medicine and Public Health.
Crane emphasized that these results come from an observational study: “What we found was that people with higher levels of glucose had a higher risk of dementia, on average, than did people with lower levels of glucose,” he said. “While that is interesting and important, we have no data to suggest that people who make changes to lower their glucose improve their dementia risk. Those data would have to come from future studies with different study designs.”
More research is planned to delve into various possible mechanisms for the relationship between blood sugar and dementia. “This work is increasingly relevant,” Crane said, “because of the worldwide epidemics of dementia, obesity, and diabetes.”
Read about the study in the New England Journal of Medicine and the New York Times.