title: Cerebral oxygenation in wake and during sleep and its relationship to cognitive function in community-dwelling older adults without sleep disordered breathing.
abstract: BACKGROUND
  This descriptive cross-sectional study investigated the relationships between cerebral oxygen reserve and cognitive function in community-dwelling older adults.
  
  
  METHODS
  Participants (72 women and 40 men) underwent standard polysomnography, including regional measures of percent oxyhemoglobin saturation (rcSO(2)) determined by cerebral oximetry. Two variables were used to calculate cerebral oxygen reserve: (a) awake rcSO(2) (mean presleep rcSO(2)) and (b) the change in rcSO(2) from before sleep to the end of the first non-rapid-eye movement cycle. General linear models, adjusted for the effects of education and occupation, tested differences in performance on standard tests of memory, attention, and speed of mental processing.
  
  
  RESULTS
  Awake rcSO(2) values were normal (60%-79.9%) in 64 participants, marginal (50%-59.9%) in 41, and low (43%-49.9%) in 7. Participants with normal awake levels had higher cognitive function than those with low levels (p < .05). Changes in rcSO(2) were greatest in participants with marginal awake rcSO(2) values; among whom, those who increased rcSO(2) during sleep (n = 17) had better memory function than the 24 who did not (p < .05).
  
  
  CONCLUSIONS
  Low awake rcSO(2) values mark individuals with low cerebral oxygen reserves and generally lower cognitive function; marginal awake rcSO(2) values that fall during sleep may indicate loss of cerebral oxygen reserve and an increased risk for cognitive decline. Further studies may clarify the significance of and mechanisms underlying individual differences in awake rcSO(2) and the changes that occur in rcSO(2) while asleep.
authors.affiliation: School of Nursing, The University of North Carolina at Chapel Hill, CB 7460 Carrington Hall, Chapel Hill, NC 27599, USA. bcarlson@email.unc.edu
authors.forename: Barbara W
authors.initials: BW
authors.lastname: Carlson
authors.forename: Virginia J
authors.initials: VJ
authors.lastname: Neelon
authors.forename: John R
authors.initials: JR
authors.lastname: Carlson
authors.forename: Marilyn
authors.initials: M
authors.lastname: Hartman
authors.forename: Donald L
authors.initials: DL
authors.lastname: Bliwise
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000378:metabolism*; D003071:Cognition; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D020925:Hypoxia-Ischemia, Brain / Q000209:etiology; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D012890:Sleep / Q000502:physiology*; D012891:Sleep Apnea Syndromes / Q000378:metabolism; D014851:Wakefulness / Q000502:physiology*
chemical_list: D010100:Oxygen