title: Change in sleep duration and cognitive function: findings from the Whitehall II Study.
abstract: OBJECTIVE
  Evidence from cross-sectional studies shows that sleep is associated with cognitive function. This study examines change in sleep duration as a determinant of cognitive function.
  
  
  METHODS
  Prospective cohort.
  
  
  METHODS
  The Whitehall II study.
  
  
  METHODS
  1459 women and 3972 men aged 45-69 at baseline.
  
  
  METHODS
  None.
  
  
  RESULTS
  Sleep duration (≤ 5, 6, 7, 8, ≥ 9 h on an average week night) was assessed once between 1997-1999, baseline for the present study, and once between 2002-2004, average follow-up 5.4 years. Cognitive function was measured (2002-2004) using 6 tests: verbal memory, inductive reasoning (Alice Heim 4-I), verbal meaning (Mill Hill), phonemic and semantic fluency, and the Mini Mental State Examination (MMSE). In analyses adjusted for age, sex, and education, and corrected for multiple testing, adverse changes in sleep between baseline and follow-up (decrease from 6, 7, or 8 h, increase from 7 or 8 h) were associated with lower scores on most cognitive function tests. Exceptions were memory, and, for a decrease from 6-8 h only, phonemic fluency. Further adjustment for occupational position attenuated the associations slightly. However, firm evidence remained for an association between an increase from 7 or 8 h sleep and lower cognitive function for all tests, except memory, and between a decrease from 6-8 h sleep and poorer reasoning, vocabulary, and the MMSE. The magnitude of these effects was equivalent to a 4-7 year increase in age.
  
  
  CONCLUSIONS
  These results suggest that adverse changes in sleep duration are associated with poorer cognitive function in the middle-aged.
authors.affiliation: University College London, Department of Epidemiology and Public Health, London, UK. j.ferrie@ucl.ac.uk
authors.forename: Jane E
authors.initials: JE
authors.lastname: Ferrie
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Shipley
authors.forename: Tasnime N
authors.initials: TN
authors.lastname: Akbaraly
authors.forename: Michael G
authors.initials: MG
authors.lastname: Marmot
authors.forename: Mika
authors.initials: M
authors.lastname: Kivimäki
authors.forename: Archana
authors.initials: A
authors.lastname: Singh-Manoux
mesh_terms: D000367:Age Factors; D000368:Aged; D016009:Chi-Square Distribution; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000150:complications / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D009483:Neuropsychological Tests; D011446:Prospective Studies; D012044:Regression Analysis; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications / Q000503:physiopathology; D013997:Time Factors