title: Night-to-night sleep variability in older adults with and without chronic insomnia.
abstract: OBJECTIVE
  (1) To quantify night-to-night variability in sleep behaviors and sleep measures among older chronic insomnia (CI) subjects and non-insomnia (NI) controls; (2) to investigate systematic temporal patterns of sleep behaviors and sleep measures across nights; and (3) to examine clinical correlates of sleep variability.
  
  
  METHODS
  Sixty-one older adults with CI (71.4years old, 67% F) and 31 older adults with NI (70.7years old, 65% F) completed questionnaires, kept sleep diaries and wore wrist actigraphs for 2 weeks. Mixed models were used to estimate within-subject mean and standard deviation values; these were then compared across groups. Mixed models were also used to determine associations across nights of sleep measures.
  
  
  RESULTS
  CI and NI differed on mean values for clinical ratings and sleep diary measures, but not for actigraphy measures. CI also showed significantly greater variability than NI on most sleep diary measures and on actigraphically measured wakefulness after sleep onset (WASO) and sleep efficiency. Among CI, neither diary nor actigraphy measures from one night correlated with values from the previous night. Diary WASO, sleep time, actigraphy sleep latency and sleep time, however, positively correlated with values from the previous two nights. Variability measures were not correlated with other global clinical measures among CI.
  
  
  CONCLUSIONS
  Compared to NI, older adults with CI report worse sleep and greater night-to-night variability, which was confirmed with actigraphy. There was little evidence for positive or negative correlation of sleep measures across nights. Variability of sleep may be an important target for insomnia treatments.
authors: Sleep Medicine Institute and Neuroscience Clinical and Translational Research Center, Department of Psychiatry, School of Medicine, University of Pittsburgh, PA 15213, USA. buyssedj@upmc.edu
authors: Daniel J
authors: DJ
authors: Buysse
authors: Yu
authors: Y
authors: Cheng
authors: Anne
authors: A
authors: Germain
authors: Douglas E
authors: DE
authors: Moul
authors: Peter L
authors: PL
authors: Franzen
authors: Mary
authors: M
authors: Fletcher
authors: Timothy H
authors: TH
authors: Monk
mesh_terms: D056044:Actigraphy; D000367:Age Factors; D000368:Aged; D002908:Chronic Disease; D002940:Circadian Rhythm; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D012016:Reference Values; D007319:Sleep Initiation and Maintenance Disorders / Q000175:diagnosis / Q000453:epidemiology*; D013223:Statistics as Topic; D014481:United States