Low blood sugar events increase dementia risk in elderly patients with Type 2 diabetes, study finds

OAKLAND, Calif. Hypoglycemic episodes that require a visit to the hospital are associated with increased risk of dementia in elderly patients with Type 2 diabetes mellitus, according to a Kaiser Permanente Division of Research study in the Journal of the American Medical Association.

Though not a randomized clinical trial, this study provides additional information for the debate about how tightly blood sugar should be controlled in patients with Type 2 diabetes, particularly in elderly patients, the researchers reported. The study appears in the current diabetes mellitus themed issue of JAMA.

While several studies have shown low blood sugar to affect cognitive function in children with Type 1 diabetes, this is the first study to evaluate the association in older patients with diabetes.

“We know that the brain becomes more vulnerable with age, and we need a better understanding of how glycemic control can affect brain health over the long term,” said the study’s principal investigator, Rachel A. Whitmer, Ph.D., a research scientist with the Kaiser Permanente Division of Research. “This study adds to the evidence base that perhaps we should rethink the notion of very tight glycemic control for our elderly patients with diabetes mellitus.”

The study looked at 16,667 elderly patients with Type 2 diabetes from the Kaiser Permanente Northern California Diabetes Registry. The average age for the study population was 66 years; 55% were male and 60% were white. The researchers identified 1,465 patients in the cohort that were hospitalized or had emergency room admittance at least once for hypoglycemia from 1980 to the end of 2002.

Compared with those with no hypoglycemic episodes, patients with one hypoglycemic episode had a 45% increased risk of being diagnosed with dementia after 2003, the study revealed. Those with two episodes had a 115% increased risk, and those with three or more episodes had a 160% increased risk of dementia. Adjustments were made for age, body mass index, race, education, gender, and duration of diabetes. The effect remained after further adjustments for hypertension, stroke, cardiovascular disease, end-stage renal disease, glycosylated hemoglobin levels, and treatment for diabetes.

Compared with those with no hypoglycemic episodes, those with one or more episode had a 32% greater risk of dementia (adjusted for age, body mass index, education, gender, duration of diabetes, co-morbidities, glycosylated hemoglobin and treatment for diabetes).

“Our findings suggest that pursuit of ‘tight’ glycemic control (i.e. to hemoglobin A1c levels less than 7%) may be inadvisable in older patients with Type 2 diabetes if required treatment is causing hypoglycemia,” said Joe Selby, MD, MPH, a co-author on this study and the director of the Kaiser Permanente Division of Research.

In view of these three trials, recent recommendations from the American Heart Association and the American College of Cardiology have urged that treatment be individualized and that caution be exercised to prevent severe hypoglycemia. The guidelines further emphasize the critical importance of blood pressure control, lipid or cholesterol control, smoking cessation, and use of aspirin, Selby said.