title: Do sleep, stress, and illness explain daily variations in fatigue? A prospective study.
abstract: OBJECTIVE
  Fatigue is related to a number of serious diseases, as well as to general well-being. It is also a major cause of sickness absence and use of health facilities. Still, the determinants of variations in fatigue are little investigated. The purpose of present study was to investigate the relationships between the daily variations of fatigue with sleep during the previous night, stress or disease symptoms during the same day - across 42 consecutive days of normal life.
  
  
  METHODS
  50 individuals participated and gave diary reports and used an actigraph across the 42days. The data was analyzed using a multilevel approach with mixed model regression.
  
  
  RESULTS
  The analyses showed that the day-to-day variation in fatigue was related to (poor) sleep quality (p<.001) and (reduced) sleep duration (p<.01) the previous night, as well as to higher stress (p<.05), and to the occurrence of a cold or fever (p<.001) during the same day as the fatigue rating. Fatigue was also strongly related to poorer subjective health (p<.001) and sleepiness (p<.001) during the same day.
  
  
  CONCLUSIONS
  The results indicate that prior sleep (and sleepiness) as well as stress and illness are consistently connected to how fatigue is experienced during normal living conditions.
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, Sweden; Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden. Electronic address: torbjorn.akerstedt@stress.su.se.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Akerstedt
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden.
authors.forename: John
authors.initials: J
authors.lastname: Axelsson
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, Sweden; Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Lekander
authors.affiliation: Institute for Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
authors.forename: Nicola
authors.initials: N
authors.lastname: Orsini
authors.affiliation: Stress Research Institute, Stockholm University, Stockholm, Sweden; Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden.
authors.forename: Göran
authors.initials: G
authors.lastname: Kecklund
mesh_terms: D000328:Adult; D004194:Disease / Q000523:psychology; D005221:Fatigue / Q000209:etiology* / Q000523:psychology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012890:Sleep; D012894:Sleep Stages; D012893:Sleep Wake Disorders / Q000150:complications / Q000175:diagnosis; D013315:Stress, Psychological / Q000150:complications*; D013997:Time Factors
keywords: Daily; KSS; Mixed model; SRH; Sleep quality; Stress; Subjective health; TST