Changes in cognitive function and brain glucose metabolism in elderly women with subjective memory impairment: a 24-month prospective pilot study

Objectives: Subjective memory impairment (SMI) may precede mild cognitive impairment (MCI) stage and would offer an earlier therapeutic opportunity than MCI would. However, it is not clear whether complaints of forgetfulness are truly reflective of objective memory dysfunction or of impairments in other cognitive domains. The aim of this current longitudinal study was to investigate changes in various cognitive functions and in regional cerebral metabolic rate of glucose (rCMRglc) among elderly women with SMI. Materials and methods: Clinical evaluation, comprehensive neuropsychological test, and ¹⁸F-fluoro-2-deoxyglucose positron emission tomography scans were conducted on 24 women with SMI at the baseline and 24-month follow-up. Changes in the cognitive domain scores and rCMRglc were assessed, and the relationships between them were analyzed. Results: All participants stayed in SMI all the way till the follow-up, not converted to MCI or dementia. A significant reduction in executive function was found (mean difference in z-score: −0.21, P = 0.02) without changes in other cognitive domains. Declines in rCMRglc were detected in the left superior temporal gyrus, right posterior cingulate gyrus, left parahippocampal gyrus, right lingual gyrus, and right angular gyrus. The change in executive function had a positive correlation with the percent change of rCMRglc in the right posterior cingulate gyrus (β = 0.43, P = 0.02). Conclusions: Our findings suggest that elderly women with SMI symptoms should be carefully monitored for declines in executive function and related brain glucose metabolism over time.