Intersubject variability of brain glucose metabolic measurements in young normal males

This study evaluates intersubject variability on regional glucose metabolic values in a group of 50 healthy right-handed males between 20 and 40 yr of age. Methods: Brain glucose metabolism was measured using PET and 2- deoxy-2[¹⁸F]fluoro-D-glucose under resting conditions and was separately assessed for subjects in their twenties (n = 34) and those in their thirties (n = 16). Results: Regional brain metabolic values showed significant intersubject variability with coefficients of variation (CV) that ranged between 11.1% to 15.2% (twenties) and 7.2% to 12.6% (thirties). Relative measures (regional/global) were less variable than absolute measures and the CV ranged between 4.1% to 8.3% (twenties) and 3.9% to 10% (thirties). Whereas global brain metabolic rate for subjects in their twenties was not significantly different from that of subjects in their thirties, the metabolic rate in left frontal regions was significantly lower in the older subjects. Conclusion: The correlations between age and absolute and relative metabolism in the left frontal region were r = 0.438, p < 0.002 and r = 0.447, p < 0.001, respectively. This study shows significant intersubject variability for regional brain metabolic values in normal controls and documents age-related decreases in frontal metabolism that occur even in relatively young adults.