Relationship between brain oxygen metabolism and cognition in older adults

Motivation: A reduction in brain metabolism is a hallmark of neurodegeneration in Alzheimer's disease (AD), according to recent criteria for staging AD. However, alterations in brain metabolism during the preclinical phase of AD are not fully understood. Goal(s): To investigate the association between brain metabolism and cognitive performance at a very early stage of dementia, when cognition is still normal. Approach: Using non-invasive MRI, we measured cerebral metabolic rate of oxygen (CMRO2) and examined its association with cognitive test scores. Results: CMRO2 was lower in participants with MCI/dementia compared to those cognitively unimpaired. However, among the unimpaired group, CMRO2 was inversely associated with cognition. Impact: The present work suggests that, at the very early stage of Alzheimer's disease, higher brain oxygen metabolism is a sign of lower cognitive function, reflecting brain's hypermetabolism/hyperactivity during preclinical neurodegeneration.