SAN FRANCISCO -- Postmenopausal women with chronically elevated blood sugar had a nearly fourfold risk of mild cognitive impairment over four years compared with women with blood sugar in the normal range.
•Explain to patients that this and other studies have found a link between chronically elevated blood sugar and mild cognitive impairment or dementia, especially among older people.
•Explain that it's essential for maintaining overall health to keep blood glucose levels, as measured by glycosylated hemoglobin (HbA1c) below 7%.
SAN FRANCISCO, Aug. 10 -- Chronically elevated blood glucose saps cognitive function in older women, according to researchers here.
Postmenopausal women with glycosylated hemoglobin (HbA1c) levels of 7% or higher had a fourfold risk of mild cognitive impairment or dementia over four years compared with women with HbA1c lower than 7%, reported Kristine Yaffe, M.D., of the University of California San Francisco and colleagues, in the current issue of the Journal of Nutrition, Health and Aging.
"We already know there's a connection between diabetes and cognitive problems," said Dr. Yaffe. "We were interested in what this measurement [HbA1c] would tell us about a group of women with and without diabetes who were followed for four years. Nobody has really looked at that before."
The American Diabetes Association recommends maintaining HbA1c levels below 7%. The American Association of Clinical Endocrinologists recommends HbA1c levels at 6.5% or below.
The investigators conducted a four-year prospective study of 1,983 postmenopausal women with osteoporosis who had HbA1c levels measured at baseline.
The women, 53 of whom were known to be diabetic at baseline, had a mean age of 67.2 years. The investigators followed these women for signs of mild cognitive impairment or dementia over the study period as part of a dementia ancillary study. The analysis included risk for dementia or mild cognitive impairment potentially associated with every 1% increase in HbA1c, and risk associated with HbA1C of 7% or greater.
The mean level of HbA1c was 5.8% at baseline, ranging from 3.0% to 12.1%. Over the course of the study, 86 women (4.3%) developed mild cognitive impairment or dementia.
The authors found that for every 1% increase in HbA1c, women had a greater age-adjusted likelihood of developing mild cognitive impairment (odds ratio 1.50, 95% confidence interval, 1.14-1.97) and of developing MCI or dementia (odds ratio 1.40, 95% CI 1.08- 1.83).
For the 49 women with HbA1c levels of 7% or higher at baseline, the age-adjusted risk for developing mild cognitive impairment was increased nearly fourfold (odds ratio 3.70, 95% CI 1.51-9.09) and nearly threefold for developing either mild cognitive impairment or dementia (odds ratio 2.86; 95% CI 1.17-6.98).
When the 53 women with diabetes were excluded from the analysis, the association between HbA1c and mild cognitive impairment was a little less robust, but still elevated, the authors reported. The unadjusted odds ratio for mild cognitive impairment among the women without diabetes was 1.59 (95% CI, 1.01-2.50). The age-adjusted odds ratio in this group was 1.42 (95% CI, 0.89-2.28).
In addition, in multivariate analyses adjusted for age, education level, race, depression, alcohol use, and treatment with raloxifene, the association between HbA1c and cognitive impairment was similar, the investigators reported.
"Type 2 diabetes is a very common and growing problem," Dr. Yaffe said. "The point is that now you can identify people who are at risk for mild cognitive impairment or dementia and monitor them closely with glycosylated hemoglobin. I think we need to take these people who are at risk and see whether we can target them for trials or interventions for better blood glucose control."