title: Sleep quality and cognitive function in healthy old age: the moderating role of subclinical depression.
abstract: OBJECTIVE
  Previous research has yielded inconclusive results on the relationship between self-reported sleep quality and cognitive performance in healthy old age. Discrepant findings have been reported regarding processing speed and attention, executive functions, and episodic memory. However, sleep quality has also been found to be related to cognitive performance in patients with depression. Our aim was to clarify the relationship between sleep quality and cognitive performance in healthy older adults, and to evaluate the moderating role of subclinical depression on this relationship.
  
  
  METHODS
  The Pittsburgh Sleep Quality Index was used to assess subjective sleep quality in 107 participants (age ≥ 61 years). A broad battery of neuropsychological tests measured basic cognitive processes, executive functions, and memory processes.
  
  
  RESULTS
  Subclinical depression moderated the link between sleep quality and cognitive performance. More precisely, poorer sleep quality was associated with lower performance in reasoning, semantic fluency, and shifting in those with high versus low levels of subclinical depression.
  
  
  CONCLUSIONS
  Our findings suggest that poor sleep quality might affect higher order cognitive processes, particularly in those reporting higher levels of subclinical depression. Findings on the relationships between sleep quality, cognitive functioning, and depressive symptomatology are discussed in relation to neurobehavioral theories of sleep.
authors.affiliation: Department of Psychology, University of Zurich, Zurich, Switzerland. c.sutter@psychologie.uzh.ch
authors.forename: Christine
authors.initials: C
authors.lastname: Sutter
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Zöllig
authors.forename: Mathias
authors.initials: M
authors.lastname: Allemand
authors.forename: Mike
authors.initials: M
authors.lastname: Martin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology* / Q000523:psychology; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000503:physiopathology; D003863:Depression / Q000503:physiopathology*; D015987:Effect Modifier, Epidemiologic; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D012890:Sleep / Q000502:physiology*; D007319:Sleep Initiation and Maintenance Disorders / Q000503:physiopathology / Q000523:psychology; D011795:Surveys and Questionnaires