“Higher glucose levels may be a risk factor for dementia,” report the thirteen authors of a National Institutes of Health-funded study, “even among persons without diabetes.”
But the takeaway for the health conscious, given that the risk increases identified are not great compared to other factors, is that higher than average blood sugar levels may be subtly affecting optimal brain function, leading to decline over time. A diagnosis of clinical dementia is, after all, a mental Rubicon. Leading up to that is a lot of shaky memory and thinking errors, in which daily glycemic levels have already been implicated.
The new study, titled “Glucose Levels and Risk of Dementia” and published in the New England Journal of Medicine, is based on a study of 2,067 Group Health patients 65 years of age and older — 232 with diabetes.
Researchers were associated with the Group Health Research Institute, VA Puget Sound Health Care System, University of Washington, and the Swedish Neuroscience Institute — all in Seattle — in addition to Massachusetts General Hospital, Harvard Medical School, Harvard School of Public Health, and Wake Forest School of Medicine.
Patients’ blood glucose levels were tracked for a median of 6.8 years — that’s more than 35,000 fasting and random tests, in addition to glycated hemoglobin tests — during which time, about 25 percent developed some form of dementia, Alzheimer’s in the majority. (Lead author Dr. Paul Crane notes, though, that in older patients “most dementias have mixed pathologies.” Pure vascular dementia, he says, is fairly rare, but it’s often a component of a broader dementia diagnosis.)
Among those without diabetes, higher than average blood sugar levels meant the “hazard ratio” for dementia increased by 18 percent. (Specifically, for the range of 105 to 115 mg/dL, dementia risk jumped from 10 to 18 percent.) For people with diabetes, glucose levels above 190 mg/dL correlated with a 40 percent increase in risk. At 95 mg/dL and below, you were sitting pretty.
Because the study was set up to answer a single question (“Do higher glucose levels increase the risk of dementia?”), it can’t be used as proof that you should lower your blood sugar levels, even if you’re not at risk of diabetes. The mechanism behind the risk has yet to be explained. (Research continues on useful biomarkers that can set off alarms earlier in the course of dementia.) But if you were considering exercising more and talking to a nutritionist, you wouldn’t be making an irresponsible inference.
