MADRID — Tight control of blood glucose levels may decrease the incidence of dementia and Alzheimer's disease among patients with diabetes, and even among those with borderline diabetes, researchers reported at the 10th International Conference on Alzheimer's Disease and Related Disorders.
The findings speak volumes about the need for early implementation of significant lifestyle changes among those at risk for diabetes, especially in light of the ongoing obesity epidemic, said Dr. Ronald Petersen, who moderated a press conference on the studies. “The number of people with Alzheimer's, and the number who will soon get it, is rising dramatically as the baby boomers turn 50,” said Dr. Petersen, vice chair of the Alzheimer's Association's Medical and Scientific Advisory Council. ¨Will this growth be redoubled by the rising tide of obesity and diabetes?”
Glycemic control is a crucial factor in protecting diabetic patients from dementia, said Rachel Whitmer, Ph.D., of Kaiser Permanente, Oakland, Calif. Her population-based study included 22,852 members of Kaiser's Northern California Diabetes Registry, who were surveyed from 1994 to 1996. The patients' mean age at baseline was 66 years; 66% were white, 10% black, and the rest were Hispanic, Asian, or Native American.
The patients were followed until 2005. By then, 11% had developed new-onset dementias. Hemoglobin A1c (HbA1c) was significantly associated with the incidence of dementia. Patients with the highest HbA1c (15% and higher) were the most likely to develop dementia, with an elevated risk of 78% compared with those whose levels were below 10%. Diabetic patients are advised to keep their HbA1c below 7%.
Those with HbA1c levels of 12%–15% were 22% more likely to develop dementia, while those whose levels were between 10% and 11.9% had a 16% increased risk. The increased risks remained significant even after adjusting for age, race, gender, weight, and diabetes treatment.
“This shows us that tight glycemic control continues to be as important as patients' age,” Dr. Whitmer said at the meeting, presented by the Alzheimer's Association. “And it will become more and more important as we experience the epidemic of obesity.”
Even patients with borderline diabetes should be aware of controlling their glucose levels, said Dr. Laura Fratiglioni, who presented research completed by her colleague, Dr. Weili Xu of the Karolinska Institute, Stockholm.
Their 9-year study tracked the incidence of dementia in 1,173 subjects older than 75 years who were free of both dementia and diabetes at baseline.
The subjects were examined three times during the study period; each exam included a blood glucose test and testing for dementia and Alzheimer's disease.
The mean follow-up was 5 years per person. By that time, borderline diabetes had been identified in 47 subjects and 397 had been diagnosed with dementia (307 with Alzheimer's).
After controlling for vascular risk factors, borderline diabetes was associated with a 67% increased risk for developing a dementia and a 77% increased risk for developing Alzheimer's, Dr. Fratiglioni said. Additional analysis found that the risk was increased yet again in those with borderline diabetes who also had a systolic blood pressure of 180 mm Hg or higher.