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

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. 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. 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). Sleep disturbance and depression significantly impacted adherence rates during chemotherapy. Results warrant attention when promoting adherence to BT sleep interventions during chemotherapy treatment.