One-Carbon Metabolism and Other Biochemical Correlates of Cognitive Impairment as Visualized by Principal Component Analysis

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Abstract
In the present report, 101 ambulatory elderly patients complaining about cognitive disturbances were investigated using the Mini-Mental State Examination (MMSE). Laboratory investigations, brain imaging, and electroen cephalography were performed. Twelve patients were diagnosed with subjective memory complaints (SMC), 32 with mild cognitive impairment (MCI), 43 with dementia of the Alzheimer type (DAT), and 14 with vascular dementia (VAD). Thirty-three percent of the SMC group, 31% of the MCI group, 45% of the DAT group, and 62% of the VAD group had increased serum homocysteine (s-HCY). Principal component analysis of 19 variables showed 3 signifi cant principal components by cross-validation. The cognitive impairment in the patients (MMSE) was explained to 50%. According to the principal component analysis, the population followed two different routes to cognitive impair ment : one correlated with disturbance of one-carbon metabolism (cerebrospinal fluid vitamin B12, plasma B12, plasma folate, and s-HCY) and the other correlated with more classic dementia, as marked by cerebrospinal fluid tau, vas cular risk factors, atrophy on brain imaging, possession of the apolipoprotein E4 allele, and age. There was poor discrimination between DAT and VAD. (J Geriatr Psychiatry Neurol 2001; 14:109-114).