| Introduction. The disruption of circadian rhythms via shift work or by other means has been associated with increased cancer risks. Many symptoms of circadian disruption including fatigue, sleep disruption and depression are associated with inflammatory cytokine secretion. While inflammation is a established risk factor for cancer development, few studies have attempted to determine whether the association between circadian disruption and cancer is driven by the secretion of inflammatory cytokines. This study sought to investigate this possibility among patients at the Dorn VA Medical Center in Columbia, SC.;Methods. Mean cytokine concentrations were compared among patients with elevated fatigue (Multidimensional Fatigue Inventory), depressive symptoms (Beck Depression Inventory II), or sleep disruption (Pittsburg Sleep Quality Index or PSQI). Mean cytokine concentrations of IL-6, TNF-alpha, INF-gamma, IL-1ra, IL-1beta, and VEGF were also compared among patients grouped by clock gene polymorphisms that have been associated with circadian disruption symptoms or cancer risk. Further analyses of racial subgroups were conducted to determine if these processes may influence the racial cancer disparity that exists among African Americans compared with European Americans.;Results. Poor sleep and higher fatigue scores were associated with increased VEGF and TNF-alpha concentrations, respectively. Participants with extra copies of the Per3 variable number tandem repeat clock gene polymorphism had higher mean interleukin-6 (IL-6) cytokine concentrations compared to those without this polymorphism. African Americans with this genotype had higher PSQI scores and elevated mean IL-6, tumor necrosis factor alpha (TNFalpha), and gamma interferon (INF-gamma) concentrations compared to European Americans.;Discussion. The findings provide some support for our hypothesis. The biological processes underlying the association between circadian disruption and cancer remain to be fully elucidated, but may involve increased inflammatory cytokine secretion. |
