A systematic review of brain metabolite changes, measured with 1H magnetic resonance spectroscopy, in healthy aging.

Background: (1)H MR spectroscopy (MRS) can identify metabolite abnormalities in age-related, neurological diseases. However, there is little information on how metabolites change with healthy aging.

Methods: We systematically reviewed the literature on MRS, from 1980 to 2006, for studies where healthy young subjects (<60 years) were compared to healthy older subjects (>60 years). We extracted metabolite data reported as "no change", "increase" or "decrease" for each metabolite by brain region and, where data were available, meta-analysed mean metabolite concentrations (mM) for young versus old subjects.

Results: Eighteen studies met the inclusion criteria (total n=703 subjects, 284 >60 years old). Most data came from the frontal region, and reported "no change" in older subjects; however, a meta-analysis revealed a decrease in frontal NAA (p=0.05) and increases in parietal choline (p=0.003) and creatine (p<0.001).

Discussion: These data suggest that NAA may decrease and choline and creatine increase with age. Therefore, more data are needed from older subjects to characterise age effects better and ratios in older subjects should be interpreted with caution.