The Association Between Circadian Disruption in Core Body Temperature Rhythm and Post‐Chemotherapy Sleep Disturbances in Breast Cancer Survivors

Sleep disturbance is a common symptom experienced by approximately 70% of breast cancer survivors and persists after the conclusion of chemotherapy. This study aimed to quantify the circadian disruption of the core body temperature (CBT) rhythm and its correlation with sleep disturbance following chemotherapy. In a sample of 25 breast cancer survivors, CBT was measured using an ingestible thermometer pill to calculate the relative amplitude (RA) prior to chemotherapy. The Pittsburgh Sleep Quality Index (PSQI) was employed to assess global sleep quality at three time points: prior to the commencement of chemotherapy, at 1 month (T1) and 9 months (T2) following the conclusion of chemotherapy. Subjective and objective sleep latency (SL_s and SL_o) were measured using the PSQI and actigraphy, respectively. The lower RA group exhibited higher intradaily variability of CBT and a higher average temperature of the lowest 5-h period in comparison to the higher RA group. The lower RA group exhibited lower global sleep quality than the higher RA group at both time points (T1 and T2). SL_s in the lower RA group were significantly longer compared to the higher RA group at both time points. Furthermore, the discrepancy in SL (∆SL_s-SL_o) demonstrated a notable between-group difference at both time points. The findings of this study suggest that breast cancer survivors with pronounced circadian disruption of the CBT rhythm prior to chemotherapy are more prone to sleep disturbances following chemotherapy. Additionally, prolonged SL_s may be a contributing factor to their poor sleep quality. Trial Registration: clinicaltrials.gov: NCT04364347.