Preliminary evidence of an association between a functional interleukin-6 polymorphism and fatigue and sleep disturbance in oncology patients and their family caregivers.
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.
Miaskowski
Christine
C
Department of Physiological Nursing, School of Nursing, University of California, San Francisco, CA 94143-0610, USA. chris.miaskowski@nursing.ucsf.edu
Dodd
Marylin
M
Lee
Kathryn
K
West
Claudia
C
Paul
Steven M
SM
Cooper
Bruce A
BA
Wara
William
W
Swift
Patrick S
PS
Dunn
Laura B
LB
Aouizerat
Bradley E
BE
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
D015850:Interleukin-6