Circadian activity rhythms and fatigue of adolescent cancer survivors and healthy controls: a pilot study

Study Objectives: The primary objective of this study was to compare circadian activity rhythms (CARs) of adolescents within 5 years of completing cancer treatment (survivors) with that of healthy adolescent controls. Secondary objectives were to explore differences in the relationship of CARs and fatigue between survivors and controls and between early survivors (<12 months posttreatment) and late survivors (>= 12 months posttreatment). Methods: Twenty-nine survivors and 30 controls, aged 13-18 years, participated in this prospective, descriptive pilot study. Adolescents and their parents completed a baseline measure of adolescents' fatigue. Adolescents wore a wrist actigraph continuously for 7 days and concurrently kept a sleep diary. Activity data recorded by actigraphy were fitted to an extended cosine model to calculate six CAR variables: acrophase, amplitude, midline estimating statistic of rhythm (MESOR), up-MESOR, down-MESOR, and F-statistic. Linear mixed models explored the relationship between CARs and fatigue. Results: There were no group differences on CAR or fatigue measures. Among survivors, earlier down-MESOR was associated with greater parent-reported fatigue (P = .020), and earlier acrophase (P = .023) and up-MESOR (P = .025) were associated with greater adolescent-reported fatigue. Significant CAR-by-time posttreatment interaction effects were found on fatigue between early and late survivors. Among controls, greater parent-reported fatigue was associated with greater MESOR (P = .0495). Conclusions: Survivors within the first 5 years posttreatment were similar to controls in CARs and fatigue, suggesting robust recovery of circadian rhythms posttreatment. Different CAR characteristics were associated with fatigue in survivors and controls. Time posttreatment influenced the relationship between CARs and fatigue for survivors, with significant effects only for early survivors.