Predictors of adherence to a behavioral therapy sleep intervention during breast cancer chemotherapy

Background: This study's purpose was twofold: (1) to establish adherence rates to a behavioral therapy (BT) sleep intervention and (2) to identify psychological and physical symptom predictors of adherence to the intervention in women undergoing breast cancer chemotherapy. Methods: A randomized controlled trial began 48 h before the first of four chemotherapy treatments. Women with stages I-IIIA breast cancer (n = 113) received a BT sleep intervention composed of stimulus control, modified sleep restriction (MSR), relaxation therapy (RT), and sleep hygiene counseling components. A BT plan was developed by a research nurse and each participant, reinforced on day 8, and repeated for chemotherapy cycles 2, 3, and 4. Adherence to the BT plan was measured daily; total adherence score was computed at each chemotherapy cycle by combining adherence estimates of all BT plan components. Psychological and physical symptoms over the past 7 days were measured 2 days prior to and 7 days after each chemotherapy treatment. Results: Total adherence rates to the BT plan were 51-52% at all four treatments but adherence varied by component. Sleep disturbance, pain, and anxiety significantly decreased whereas depression significantly increased across chemotherapy. Structural equation modeling revealed a good model fit with decreasing sleep disturbances (0.409) and increasing depression (-0.711) contributing to lower total adherence rates. Increasing depression predicted lower MSR adherence (-0.203) and decreasing sleep disturbances predicted lower RT adherence (1.220). Conclusions: Sleep disturbance and depression significantly impacted adherence rates during chemotherapy. Results warrant attention when promoting adherence to BT sleep interventions during chemotherapy treatment.