title: Brain energy metabolism and blood flow differences in healthy aging.
abstract: Cerebral metabolic rate of oxygen consumption (CMRO(2)), cerebral blood flow (CBF), and oxygen extraction fraction (OEF) are important indices of healthy aging of the brain. Although a frequent topic of study, changes of CBF and CMRO(2) during normal aging are still controversial, as some authors find decreases of both CBF and CMRO(2) but increased OEF, while others find no change, and yet other find divergent changes. In this reanalysis of previously published results from positron emission tomography of healthy volunteers, we determined CMRO(2) and CBF in 66 healthy volunteers aged 21 to 81 years. The magnitudes of CMRO(2) and CBF declined in large parts of the cerebral cortex, including association areas, but the primary motor and sensory areas were relatively spared. We found significant increases of OEF in frontal and parietal cortices, excluding primary motor and somatosensory regions, and in the temporal cortex. Because of the inverse relation between OEF and capillary oxygen tension, increased OEF can compromise oxygen delivery to neurons, with possible perturbation of energy turnover. The results establish a possible mechanism of progression from healthy to unhealthy brain aging, as the regions most affected by age are the areas that are most vulnerable to neurodegeneration.
authors.affiliation: Department of Nuclear Medicine and PET Centre, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Joel
authors.initials: J
authors.lastname: Aanerud
authors.forename: Per
authors.initials: P
authors.lastname: Borghammer
authors.forename: M Mallar
authors.initials: MM
authors.lastname: Chakravarty
authors.forename: Kim
authors.initials: K
authors.lastname: Vang
authors.forename: Anders B
authors.initials: AB
authors.lastname: Rodell
authors.forename: Kristjana Y
authors.initials: KY
authors.lastname: Jónsdottir
authors.forename: Arne
authors.initials: A
authors.lastname: Møller
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Ashkanian
authors.forename: Manouchehr S
authors.initials: MS
authors.lastname: Vafaee
authors.forename: Peter
authors.initials: P
authors.lastname: Iversen
authors.forename: Peter
authors.initials: P
authors.lastname: Johannsen
authors.forename: Albert
authors.initials: A
authors.lastname: Gjedde
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001921:Brain / Q000098:blood supply* / Q000378:metabolism* / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D055815:Young Adult