Aging of the adult human brain: in vivo quantitation of metabolite content with proton magnetic resonance spectroscopy.

The purpose of this study was to examine the effect of aging on brain metabolite concentrations, including N-acetyl aspartate (NAA), the major marker of neurones, using short echo proton spectroscopy. Single-voxel proton spectra (TE 30 msec, TR 2 seconds) were obtained from white and gray matter using automated software (PROBE, G.E., Milwaukee, WI). Spectra were analyzed using the variable projection technique. Thirty healthy volunteers were studied within the age range 24-89 years. No significant trend in change of concentrations of NAA, total creatine, total choline or myo-inositol were seen with age. The total creatine concentration of parietal white matter in the over 60 age group (6.5 +/- 0.3 mmol/l) was significantly higher than the under 60 age group (6.0 +/- 0.4 mmol/l:; P < 0.05). No other significant difference between the two age groups was seen. The tissue concentration of the major neuronal marker, NAA, does not decline with age. No age-related changes in the concentrations of choline and myo-inositol and occipital gray matter total creatine were observed. These results provide a normal range of values for spectroscopically detectable metabolites within the regions studied, against which neurological diseases such as Alzheimer's disease can be compared in vivo.