Human brain glucose utilization and cognitive function in relation to age

Brain oxidative metabolism was examined with positron emission tomography and [18F]2-deoxy-D-glucose in 40 healthy men aged 21 to 83 years, under conditions of reduced visual and auditory stimulation. The mean cerebral metabolic rate for glucose (CMRglc) equaled 4.6 to 4.7 mg X 100 gm-1 X min-1 and did not correlate significantly with age (p greater than 0.05). Regional cerebral metabolic rates for glucose (rCMRglc) and Q ratios (rCMRglc/CMRglc), which had lower coefficients of variation than did rCMRglc, also did not correlate with age. Hyperfrontality of cerebral metabolism was absent at all ages. Age decrements were demonstrated in the error score on the Benton Revised Visual Retention Test and in the Performance Subtest scaled score of the Wechsler Adult Intelligence Scale (WAIS) but not in the Verbal Subtest scaled score of the WAIS. The cognitive test scores did not correlate with brain metabolic rates. The results indicate that brain oxidative metabolism, when measured under resting conditions with reduced sensory input, is not reduced in relation to age in healthy men. Furthermore, no significant relations between intelligence and resting cerebral metabolism are evident.