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, Dr. Whitmer reported in her poster presentation.
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.