Dr. Alka M. Kanaya and colleagues determined the 4-year change in mental function in 999 white men and women enrolled in the Rancho Bernardo Study Cohort. The participants, who were about 70 years old on average, included some with diabetes, some with pre-diabetes, and others with neither condition.

At the beginning of the study, all of the subjects performed similarly on three cognitive tests, the team reports in the Archives of Internal Medicine.

After 4 years, diabetic women had a four-fold increased risk of a "major cognitive decline" on one of the tests, but not on the other two tests, compared with nondiabetic women.

The effect was strongest among women with evidence of poorly controlled blood glucose levels, the investigators found.
None of the men in any of the categories showed marked changes in cognitive test scores after 4 years.

The results, suggest that improved long-term glucose control may ameliorate cognitive decline in older women, but this observation still needs to be proven in a randomized controlled trial before a definitive conclusion can be drawn.