title: Shift work in nurses: contribution of phenotypes and genotypes to adaptation.
abstract: BACKGROUND
  Daily cycles of sleep/wake, hormones, and physiological processes are often misaligned with behavioral patterns during shift work, leading to an increased risk of developing cardiovascular/metabolic/gastrointestinal disorders, some types of cancer, and mental disorders including depression and anxiety. It is unclear how sleep timing, chronotype, and circadian clock gene variation contribute to adaptation to shift work.
  
  
  METHODS
  Newly defined sleep strategies, chronotype, and genotype for polymorphisms in circadian clock genes were assessed in 388 hospital day- and night-shift nurses.
  
  
  RESULTS
  Night-shift nurses who used sleep deprivation as a means to switch to and from diurnal sleep on work days (∼25%) were the most poorly adapted to their work schedule. Chronotype also influenced efficacy of adaptation. In addition, polymorphisms in CLOCK, NPAS2, PER2, and PER3 were significantly associated with outcomes such as alcohol/caffeine consumption and sleepiness, as well as sleep phase, inertia and duration in both single- and multi-locus models. Many of these results were specific to shift type suggesting an interaction between genotype and environment (in this case, shift work).
  
  
  CONCLUSIONS
  Sleep strategy, chronotype, and genotype contribute to the adaptation of the circadian system to an environment that switches frequently and/or irregularly between different schedules of the light-dark cycle and social/workplace time. This study of shift work nurses illustrates how an environmental "stress" to the temporal organization of physiology and metabolism can have behavioral and health-related consequences. Because nurses are a key component of health care, these findings could have important implications for health-care policy.
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Gamble
authors.forename: Alison A
authors.initials: AA
authors.lastname: Motsinger-Reif
authors.forename: Akiko
authors.initials: A
authors.lastname: Hida
authors.forename: Hugo M
authors.initials: HM
authors.lastname: Borsetti
authors.forename: Stein V
authors.initials: SV
authors.lastname: Servick
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Ciarleglio
authors.forename: Sam
authors.initials: S
authors.lastname: Robbins
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hicks
authors.forename: Krista
authors.initials: K
authors.lastname: Carver
authors.forename: Nalo
authors.initials: N
authors.lastname: Hamilton
authors.forename: Nancy
authors.initials: N
authors.lastname: Wells
authors.forename: Marshall L
authors.initials: ML
authors.lastname: Summar
authors.forename: Douglas G
authors.initials: DG
authors.lastname: McMahon
authors.forename: Carl Hirschie
authors.initials: CH
authors.lastname: Johnson
mesh_terms: D000222:Adaptation, Physiological; D000223:Adaptation, Psychological; D002940:Circadian Rhythm; D005838:Genotype; D006801:Humans; D009740:Nursing Staff / Q000523:psychology*; D010641:Phenotype; D011110:Polymorphism, Genetic; D012890:Sleep; D014940:Work Schedule Tolerance