Magnetic resonance spectroscopy and cognitive function in healthy elderly men

Abstract

Subtle cognitive decrements in older people are important in terms of the associated morbidity and as a risk factor for dementia. However, their pathophysiological basis is poorly understood. Proton magnetic resonance spectroscopy (1H-MRS) may provide the means to investigate early changes in brain metabolite concentrations. We examined the relationships between N-acetyl-aspartate (NAA), choline (Cho) and creatine (Cr) metabolite ratios in a voxel in the parietal cortex and cognitive function in 88 healthy, non-demented, unmedicated men aged 65-70 years. We also used linear regression to give a value for each metabolite adjusted for the levels of the other two metabolites. Both NAA/ Cr and Cho/Cr ratios correlated positively with tests of verbal memory and a verbal memory factor (e.g. NAA/ Cr and Logical Memory: r = 0.24, P < 0.05). Cho/Cr ratios also correlated positively with tests of visual memory (e.g. visual reproduction: r = 0.21, P < 0.05). Adjusted Cr levels correlated negatively and significantly with tests of verbal memory and the Verbal Memory Factor. The regression analysis suggested that Cr levels better explained the correlations between NAA/Cr and Cho/Cr ratios and cognitive variables than NAA or Cho levels. These results suggest that in healthy men aged 65-70 years, metabolite levels relate to cognitive performance. Rising Cr levels may be an early marker of cognitive decline.