In 76 normal volunteers studied by positron emission tomography, with [18F]fluorodeoxyglucose, CMR(glu) was significantly lower in the elderly as compared with young subjects and significantly higher in females relative to males. However, in 58 of these subjects who also had magnetic resonance imaging scans, age and gender were found to be unrelated to CMR(glu), when the effects of brain volume and brain atrophy on CMR(glu) were partialed out using covariate analyses. Individually, brain volume was found to have a significant effect on CMR(glu), explaining ~17% of the variability in CMR(glu) measures and brain atrophy explaining ~8% of the variance in CMR(glu). Together these two measures accounted for ~21% of the variance. Cerebrovascular risk factors in normal subjects were not found to affect mean CMR(glu) or the variability of CMR(glu) measures. In this study almost 80% of the variance in CMR(glu) could not be explained by any of the factors that had been considered. This implies a lack of sensitivity of absolute values of global CMR(glu) to the mild effects of brain dysfunction. Although some of the unexplained variance is probably methodological in origin, physiological factors that are difficult to quantify, such as the state of arousal, are likely to be contributory as well.
ASJC Scopus subject areas
- Clinical Neurology
- Cardiology and Cardiovascular Medicine