title: Preliminary evidence of an association between a functional interleukin-6 polymorphism and fatigue and sleep disturbance in oncology patients and their family caregivers.
abstract: BACKGROUND
  Fatigue and sleep disturbance are common problems in oncology patients and their family caregivers (FCs). However, little is known about factors that contribute to interindividual variability in these symptoms or to their underlying biologic mechanisms.
  
  
  OBJECTIVE
  An evaluation was done on whether genetic variation in a prominent proinflammatory cytokine, interleukin-6 (IL-6 c.-6101A>T [rs4719714]), was associated with mean ratings of evening fatigue, morning fatigue, and sleep disturbance, as well as with the trajectories of these symptoms.
  
  
  METHODS
  Over six months, participants completed standardized measures of fatigue and sleep disturbance. Linear regression was used to assess the effect of the IL-6 genotype and other covariates on mean fatigue and sleep disturbance scores. Hierarchical linear modeling was used to determine the effect of the IL-6 genotype on symptom trajectories.
  
  
  RESULTS
  Common allele homozygotes reported higher levels of evening fatigue (P=0.003), morning fatigue (P=0.09), and sleep disturbance (P=0.003) than minor allele carriers. Predictors of baseline level and trajectories of evening fatigue included age, gender, and genotype (intercepts) and baseline level of evening fatigue (slope). Predictors of baseline level and trajectories of morning fatigue included age and genotype (intercept) and age and baseline level of morning fatigue (slope). Predictors of baseline level and trajectories of sleep disturbance included age and genotype (intercept) and baseline level of sleep disturbance (slope).
  
  
  CONCLUSIONS
  Findings provide preliminary evidence of a genetic association between a functional promoter polymorphism in the IL-6 gene and severity of evening fatigue, morning fatigue, and sleep disturbance in oncology patients and their FCs.
authors.affiliation: Department of Physiological Nursing, School of Nursing, University of California, San Francisco, CA 94143-0610, USA. chris.miaskowski@nursing.ucsf.edu
authors.forename: Christine
authors.initials: C
authors.lastname: Miaskowski
authors.forename: Marylin
authors.initials: M
authors.lastname: Dodd
authors.forename: Kathryn
authors.initials: K
authors.lastname: Lee
authors.forename: Claudia
authors.initials: C
authors.lastname: West
authors.forename: Steven M
authors.initials: SM
authors.lastname: Paul
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Cooper
authors.forename: William
authors.initials: W
authors.lastname: Wara
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Swift
authors.forename: Laura B
authors.initials: LB
authors.lastname: Dunn
authors.forename: Bradley E
authors.initials: BE
authors.lastname: Aouizerat
mesh_terms: D000367:Age Factors; D000368:Aged; D000483:Alleles; D017028:Caregivers; D005221:Fatigue / Q000150:complications / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D056726:Genetic Association Studies; D005838:Genotype; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012720:Severity of Illness Index; D012737:Sex Factors; D012893:Sleep Wake Disorders / Q000150:complications / Q000235:genetics*; D011795:Surveys and Questionnaires
chemical_list: D015850:Interleukin-6