Fatigue is a frequent side effect in patients undergoing cancer chemotherapy. Patients may experience insomnia and pain, which are risk factors for fatigue, and have more severe fatigue after the introduction of chemotherapy. The present prospective cohort study included 59 patients who had been newly introduced to chemotherapy. We investigated the incidence of the severe fatigue and the influencing factors after the introduction of chemotherapy in patients with insomnia or pain prior to the introduction of chemotherapy. Patients with Visual Analog Scale (VAS) scores of < 20 mm and ≥ 20 mm were categorized into the "- group" and "+ group," respectively. A VAS score of ≥ 80 mm was considered to indicate severe fatigue, which was the primary endpoint of this study. Statistical analyses were performed using the log-rank test and the Cox proportional hazards model. The incidence of severe fatigue in the + group was always high (P = 0.011). Four factors: insomnia (adjusted HR = 17.721; P < 0.0001), cigarette smoking (adjusted HR = 31.602; P < 0.0001), alcohol use (adjusted HR = 0.119; P = 0.002), sleep-inducing drug use (adjusted HR = 0.054; P = 0.016) have been identified as risk factors contributing to the occurrence of severe fatigue. The results of the present study suggest the possibility that severe fatigue in cancer patients can be prevented by evaluating and treating symptoms such as insomnia, etc., which are risk factors for severe fatigue, prior to the introduction of chemotherapy.
