Lagged relationships among sleep disturbance, fatigue, and depressed mood during chemotherapy.

Objective: Recent research suggests that sleep disturbance, fatigue, and depressed mood form a symptom cluster in patients treated with chemotherapy. To date, however, no studies have examined lagged relationships among these symptoms during chemotherapy, a time when symptom variability is high. The aim of the current study was to examine lagged changes among daily symptoms during platinum-based chemotherapy. Method: Participants were 78 women with gynecologic cancer (mean age 63 years, SD = 11; 91% Caucasian, 97% non-Hispanic). Sleep disturbance was assessed via wrist actigraphy, whereas fatigue and depressed mood were assessed via daily diary in the week after participants' first chemotherapy infusion. Latent change score models (LCS) were used to examine lagged relationships between symptom pairs. Results: High levels of sleep disturbance (i.e., minutes awake at night) were associated with earlier subsequent peaks in fatigue, and high levels of fatigue were associated with higher subsequent levels of depressed mood. Conclusions: These findings suggest that sleep disturbance, fatigue, and depressed mood occur in a cascade pattern during chemotherapy, in which increases in sleep disturbance contribute to fatigue, which, in turn, contributes to depressed mood. Interventions targeting symptoms early in the cascade, such as sleep disturbance, may provide benefits across multiple downstream symptoms.