Abstract
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Introduction: Elderly patients with depression commonly experience cognitive dysfunction. However, they report various types of results. For instance, some of them recover their cognitive function after depression treatment, whereas some patients manifest continuation of cognitive decline as a residual symptom of depression. Some individuals even develop a progressive course of dementia. Therefore, we investigate whether regional cerebral glucose metabolism (rCMglc) and neuropsychological features are different between depressed patients with amyloid negative (MCI-) and positive (MCI+) MCI.
Methods: Total 31 depressed patients with MCI were prospectively enrolled and performed the neuropsychological test, FDG PET, Florbetaben (FBB) PET, and MRI under the standard protocol. Patients were classified into 15 MCI- and 16 MCI+ subgroups according to the amyloid positivity based on FBB PET. PET images were preprocessed using SPM12 with T1 MR images and estimated on a voxel-by-voxel basis with age, sex and education as covariates. FDG PET images were compared between MCI subgroups and 21 cognitively normal elderly (NC) group with the statistical threshold of uncorrected P-value <0.001 and extent threshold >100 continuous voxel size. The other data were analyzed using the Mann-Whitney test using SPSS software with the statistical threshold of P-value <0.05. Results Both MCI- and MCI+ groups showed significantly lower z-scores in most of the neuropsychological tests compared with NC group. Between MCI subgroups, only z scores of recall and constructional recall were significantly lower in MCI+ (-1.23±0.89 vs. -2.15±0.65, p=0.003 and -0.56±1.19 vs. -1.57±0.63, p=0.012, respectively). MCI showed lower rCMglc in the left inferior temporal, left triangular part of inferior frontal gyrus, right fusiform gyrus, right middle frontal gyrus, right angular gyrus and right medial frontal gyrus than NC. Between NC and each MCI subgroup, MCI- showed lower rCMglc in the left superior frontal gyrus, orbital part, right middle frontal gyrus, orbital part, left angular gyrus, right triangular part of inferior frontal gyrus, left inferior temporal gyrus and right middle temporal gyrus, and MCI+ showed lower rCMglc in the left parahippocampal gyrus, right precuneus, left inferior temporal gyrus, right middle temporal gyrus, left angular gyrus and left superior frontal gyrus. In MCI subgroup analysis, MCI+ group did not show lower rCMglc but only MCI- did in the left inferior frontal orbital part. Conclusion Depressed elders in the prodromal phase of Alzheimer’s disease have different cerebral metabolic activation when compared with depressed elders without amyloidopathy, even though both groups showed mild cognitive impairment. The cerebral metabolic pattern might be a useful predictive marker for the prognosis of cognitive dysfunction in depressed elders.