Disruption of sleep, sleep-wake activity rhythm, and nocturnal melatonin production in breast cancer patients undergoing adjuvant chemotherapy: prospective cohort study

Objective: This prospective cohort study captured the patterns of sleep, sleep-wake activity rhythm, and first-morning urinary melatonin in breast cancer patients undergoing adjuvant chemotherapy. Methods: Breast cancer patients undergoing adjuvant chemotherapy wore wrist actigraph for 168 h and collected first-morning void urine samples before treatment, during the first, and at the last cycle of chemotherapy. We converted actigraphy data into sleep duration, sleep efficiency, nighttime total wake time, percent rhythm, F-statistic, amplitude, mesor, and acrophase. We then assessed urinary 6-sulfatoxymelatonin (aMT6s) levels. Results: This cohort contained 180 participants. Compared with the baseline, sleep efficiency during the first and last cycle decreased by 10.16% [95% confidence interval (95% CI): 5.85%, 14.47%] and 5.01% (95% CI: 0.50%, 9.53%), respectively. Similarly, percent rhythm decreased by 27.20% (95% CI: 19.95%, 34.45%) during the first cycle and 21.20% (95% CI: 13.52, 28.89) during the last cycle. Taking the baseline as the reference, aMT6s levels during the first and last cycle decreased by 11.27% (95% CI: 0.37%, 22.16%) and 14.74% (95% CI: 2.34, 27.11), respectively. Conclusion: The first administration of adjuvant chemotherapy is associated with sleep disturbance and sleep-wake activity rhythm disruption among breast cancer patients, while the disturbance and disruption during the last cycle are less severe; nevertheless, repeated administration of chemotherapy results in progressive impairment of nocturnal melatonin production.