Neurochemical changes in the aging brain: A systematic review.

Magnetic resonance spectroscopy (MRS) holds promise for understanding neurochemical mechanisms associated with human cognitive aging in vivo. Recent advances in magnetic field strength and methods provide the opportunity to examine neurometabolites with greater accuracy and detail. The current review summarizes recent literature on age-associated neurometabolite changes as measured by proton MRS, and the associations with cognition in non-clinical populations. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, 179 studies were screened for review, of these, 42 were eligible. When a subset of studies were assessed based on voxel placement, magnetic field strength and sample size, N acetyl aspartate (NAA) concentration was consistently reduced with age predominantly in the frontal lobe and Myo-inositol (mI) concentration increased with age consistently in the posterior cingulate cortex (PCC). These findings are of particular interest as these NAA and mI changes mirror neurometabolite changes often seen in Alzheimer disease. The findings of this review provide further evidence of the potential for 1H-MRS to track age-related neurometabolite changes.