title: Associations of the 24-h activity rhythm and sleep with cognition: a population-based study of middle-aged and elderly persons.
abstract: BACKGROUND
  Cognitive functioning changes with age, sleep, and the circadian rhythm. We investigated whether these factors are independently associated with different cognitive domains assessed in middle-aged and elderly persons.
  
  
  METHODS
  In 1723 middle-aged and elderly persons (age 62 ± 9.4 years, mean ± standard deviation, SD) of the Rotterdam Study, we collected actigraphy recordings of on average 138 h. Actigraphy was used to quantify 24-h rhythms by calculating the stability of the rhythm over days and the fragmentation of the rhythm. Sleep parameters including total sleep time, sleep-onset latency, and wake after sleep onset were also estimated from actigraphy. Cognitive functioning was assessed with the word learning test (WLT), word fluency test (WFT), letter digit substitution task (LDST), and Stroop color word test (Stroop).
  
  
  RESULTS
  Persons with less stable 24-h rhythms performed worse on the LDST (B = 0.42 per SD increase, p = 0.004) and the Stroop interference trial (B = -1.04 per SD increase, p = 0.003) after full adjustment. Similarly, persons with more fragmented rhythms performed worse on the LDST (B = -0.47 per SD increase, p = 0.002) and the Stroop (B = 1.47 per SD increase, p <0.001). By contrast, longer observed sleep-onset latencies were related to worse performance on the WLT delayed recall (B = -0.19 per SD increase, p = 0.027) and the WFT (B = -0.45 per SD increase, p = 0.007).
  
  
  CONCLUSIONS
  Disturbances of sleep and the 24-h activity rhythm were independently related to cognition; while persons with longer sleep-onset latencies had worse performance on memory and verbal tasks, persons with 24-h rhythm disturbances performed less on executive functioning and perceptual speed tasks.
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Annemarie I
authors.initials: AI
authors.lastname: Luik
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Lisette A
authors.initials: LA
authors.lastname: Zuurbier
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.affiliation: Department of Sleep and Cognition, Netherlands Institute for Neuroscience, an Institute of the Netherlands Royal Academy of Arts and Sciences, Amsterdam, The Netherlands; Departments of Integrative Neurophysiology and Medical Psychology, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University and Medical Center, Amsterdam, The Netherlands.
authors.forename: Eus J W
authors.initials: EJ
authors.lastname: Van Someren
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, Rotterdam, The Netherlands; Department of Neurology, Erasmus University Medical Center, Rotterdam, The Netherlands; Department of Radiology, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: M Arfan
authors.initials: MA
authors.lastname: Ikram
authors.affiliation: Department of Epidemiology, Erasmus University Medical Center, Rotterdam, The Netherlands; Department of Child and Adolescent Psychiatry, Erasmus University Medical Center, Rotterdam, The Netherlands; Department of Psychiatry, Erasmus University Medical Center, Rotterdam, The Netherlands. Electronic address: h.tiemeier@erasmusmc.nl.
authors.forename: Henning
authors.initials: H
authors.lastname: Tiemeier
mesh_terms: D056044:Actigraphy; D000204:Activity Cycles; D000367:Age Factors; D000368:Aged; D002940:Circadian Rhythm; D003072:Cognition Disorders / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011159:Population Surveillance; D012307:Risk Factors; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications* / Q000453:epidemiology
keywords: Activity rhythm; Aging; Circadian rhythm; Cognition; Sleep