The longitudinal relationship between fatigue and sleep in breast cancer patients undergoing chemotherapy

Abstract

Study objective: Fatigue and sleep disturbances are two of the most common and distressing symptoms of cancer patients. A relationship between the two symptoms was reported in symptom cluster studies; however, only subjective measurements of sleep were examined and most studies were cross-sectional. In this study of women with breast cancer undergoing chemotherapy, we explored the longitudinal relationship between fatigue and sleep measured both subjectively and objectively.

Design: Prospective study. Data were collected at 7 time points: before (baseline) and during the 3 weeks of cycle 1 and cycle 4 chemotherapy.

Participants: Ninety-seven women with newly diagnosed stage I-III breast cancer who were scheduled to receive at least four 3-week cycles of chemotherapy.

Measurement and results: Objective sleep parameters were measured with an Actillume actigraph (Ambulatory Monitoring Inc.). Subjective sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI). Fatigue was assessed with the Multidimensional Fatigue Symptom Inventory-Short Form (MFSI-SF). Fatigue became worse during both cycles of chemotherapy (P-values < 0.01). Subjective sleep quality was poor at baseline and remained unchanged throughout treatment. Objective nighttime and daytime total sleep time increased compared to baseline during the treatment administration week of both cycles; daytime total wake time decreased during the treatment week of both cycles and during the last 2 week of cycle 4. Mixed model results revealed that fatigue was positively associated with total PSQI scores and with objective measures of total nap time, and negatively associated with total wake time during the day (all P-values < 0.01).

Conclusion: Fatigue was significantly associated with subjective reports of poor sleep and objective measures of daytime sleepiness, but not with nocturnal sleep as measured with actigraphy. This relationship between fatigue and sleep warrants further studies to explore their possible common underlying etiology.

Keywords: Breast cancer; chemotherapy; fatigue; napping; sleep.

Figure 1

Screening and enrollment flowchart.

Figure 2

Total Multidimensional Fatigue Symptom Inventory-Short Form (MFSI-SF) scores, total Pittsburgh Sleep Quality Index (PSQI) scores, nighttime total sleep time (TST), nighttime total wake time (TWT), daytime total nap time (NAPTIME) and daytime total wake time (WAKE) before and during chemotherapy (mean ± SE). C1W1, Cycle 1 Week 1; C1W2, Cycle 1 Week 2; C1W3, Cycle 1 Week 3; C4W1, Cycle 4 Week 1; C4W2, Cycle 4 Week 2; C4W3, Cycle 4 Week 3. Significant differences between each treatment time point and baseline (time effect) are indicated by: **P < 0.01, ***P < 0.0001. (A) Total MFSI-SF scores. Race and use of antacids were adjusted. Note that total MFSI-SF scores increased significantly at C1W1, C1W3, C4W1, C4W2 and C4W3 compared to its baseline. (B) Total PSQI scores. Race and using of sleeping medications were adjusted. Note that although there were no significant changes of total PSQI scores during both cycles of chemotherapy compared to its baseline, the mean total PSQI scores were > 7 at all time points. (C) TST. Race, BMI, and use of analgesics were adjusted. Note that TST increased significantly during the treatment week of both cycles (C1W1 and C4W1) compared to baseline. (D) TWT. Race and BMI were adjusted. Note that there were no significant changes of TWT during chemotherapy compared to baseline. (E) NAPTIME. Note that NAPTIME increased significantly during the treatment week of both cycles (C1W1 and C4W1) when compared to baseline. (F) WAKE. Compared to baseline, WAKE decreased significantly during the treatment week of cycle 1 (C1W1) and all weeks of cycle 4 (C4W1, C4W2 and C4W3).