A longitudinal study of measures of objective and subjective sleep disturbance in patients with breast cancer before, during, and after radiation therapy.

CONTEXT: Sleep disturbance is a significant problem in oncology patients.
OBJECTIVES: To examine how actigraphy and self-report ratings of sleep disturbance changed over the course of and after radiation therapy (RT); investigate whether specific patient, disease, and symptom characteristics predicted the initial levels and/or the characteristics of the trajectories of sleep disturbance; and compare predictors of subjective and objective sleep disturbance.
METHODS: Patients (n=73) completed self-report questionnaires that assessed sleep disturbance, fatigue, depressive symptoms, anxiety, and pain before the initiation of RT through four months after the completion of RT. Wrist actigraphy was used as the objective measure of sleep disturbance. Hierarchical linear modeling was used for data analyses.
RESULTS: Mean wake after sleep onset was 11.9% and mean total score on the General Sleep Disturbance Scale was 45. More than 85% of the patients had an abnormally high number of nighttime awakenings. Substantial interindividual variability was found for both objective and subjective measures of sleep disturbance. Body mass index predicted baseline levels of objective sleep disturbance. Comorbidity, evening fatigue, and depressive symptoms predicted baseline levels of subjective sleep disturbance, and depressive symptoms predicted the trajectory of subjective sleep disturbance.
CONCLUSION: Different variables predicted sleep disturbance using subjective and objective measures. The slightly elevated wake after sleep onset found may be an underestimation of the degree of sleep disturbance when it is evaluated in the context of the high number of nighttime awakenings and patient's perception of poor sleep quality and quantity.