A proton magnetic resonance spectroscopy study of age-related changes in frontal lobe metabolite concentrations

Ageing is associated with reduction of grey matter volume and it is reporte d that the frontal lobes are preferentially affected. We have applied quant itative magnetic resonance spectroscopy (MRS), incorporating measurement of brain tissue water content and metabolite T-2 relaxation times, to determi ne absolute concentrations of the putative neuronal marker N-acetylaspartat e (NAA), creatine (Cr) and choline (Cho) compounds in the frontal lobe of 5 0 male subjects aged between 20 and 70 years (10 per decade). The fractiona l brain water content (beta (MR)) did not change significantly as a functio n of age (r = 0.07, P = 0.65) and had a mean value of 81% (CV = 2%). The co ncentration tin millimoles per litre brain tissue) of NAA decreased signifi cantly with age (r = -0.42, P = 0.003), with an overall decrease of 12% bet ween the third and seventh decades. The concentrations of Cr and Cho did no t change significantly with age. The interpretation of the age-dependent de crease in NAA concentration as reflecting either a reduction in neuronal vo lume, number or function is discussed.