Data from a trial involving 7027 postmenopausal women showed that older women with diabetes or prediabetes have worse mental function than women with normal blood sugar levels and are at greater risk for mental decline over time. The participants were "relatively high-functioning community-dwelling women" with an average age of 66.3 years. The researchers reported their findings in Neurology (August 24, 2004). The study involved 267 participants who were classified as diabetic and 297 as having "impaired fasting glucose," meaning that they had high blood glucose levels but were not yet diabetic.
At the beginning of the 4-year study, the diabetic group had the lowest age-adjusted cognitive scores on average, but the scores of those with impaired fasting glucose also were dramatically lower, compared with the scores of women with normal glucose. As the study progressed, the diabetic women showed a significantly higher decline in mental powers than the other 2 groups, despite controlling for education, depression, and ethnicity.
The assessments showed that 24 of the diabetic participants (12%) and 22 of those with impaired fasting glucose (10%) had dementia or milder cognitive impairment. Only 6% of those with normal glucose levels were affected in this way.