- July 25 2006

Diabetic patients with HbA1c levels that are well out of control are driving down the road towards dementia.

Type 2 diabetes patients with HbA1c levels in excess of 15 have a 78% greater risk of developing dementia or Alzheimer's disease or cognitive decline in the next decade, said Rachel Whitmer, Ph.D., an investigator at Kaiser Permanente Northern California in Oakland.

Those with very poor glycemic control (HbA1c levels greater than 10) were at an increased risk of incident dementia, she said in a report at the International Conference on Alzheimer's Disease and Related Disorders here. "Strict glycemic control is important for patients with diabetes in old age."

She said that compared with the 19,318 patients who had a HbA1c less than 10, those 1,286 patients with levels between 10 and 11.9 were 16% more likely to have dementia (HR=1.16, 95% CI 1.01-1.32).

Those 1,143 patients with levels between 12 and 14.9 were 25% more likely (HR=1.25 95% CI 1.03-1.53) to have dementia. Those 105 patients with levels greater than 15 were 78% more likely (HR=1.78, 95% CI 1.01-3.65) to have dementia. She said there did not appear to be an impact on the likelihood of developing dementia if the HbA1c was less than 10.

"The least well controlled diabetics have the greatest increase in risk of dementia," commented neurologist Ronald Peterson, M.D., of the Mayo Medical School in Rochester, Minn., who moderated a press briefing as a spokesman for the Alzheimer's Association, which manages the international conference.

Dr. Whitmer said that overall an HbA1c level higher than 10 -- a level recorded by 3,316 of the patients in the study -- results in an increased risk of dementia of 28%. That was statistically significant at the P=.0003 level, she said.

In the study, 22,852 patients older than 50 who were diagnosed with type 2 diabetes were enrolled in the Kaiser Permanente of Northern California Diabetes Registry and had an HbA1c level recorded between the years 1994 and 1996.

Researchers then scrutinized the medical records of the patients for hospital codes indicating treatment for dementia between Jan. 1, 1997, and May 30, 2005, She said the fact that more that 10% of the diabetic population had HbA1c levels greater than 10 reflected the fact that many patients do not appear to be adherent in taking medicine prescribed to keep hyperinsulinemia under control.

Practice Pearls

• Explain to interested patients that this study associated poor glycemic control with the eventual development of dementia. Point out however that the study cannot prove causality.
• Explain that aside from medication lifestyle changes, especially exercise, can help control blood sugar levels.

10th International Conference on Alzheimer's Disease and Related Disorders

Abstract P1-182: glycemic control and risk of dementia in a cohort of patients with Type2 diabetes.