Comparison of fatigue and fatigability correlates in Korean breast cancer survivors and differences in associations with anxiety, depression, sleep disturbance, and endocrine symptoms: a randomized controlled trial

BACKGROUND: Fatigue is one of the most common and burdensome symptoms experienced by cancer patients. In interventions intended to reduce fatigue in such patients, fatigability, or perception of fatigue contextualized to activities of fixed intensity and duration, may also be measured. This study investigated the effects of a 15-month intervention on fatigue and fatigability in breast cancer survivors (BCS); explored the fatigue-fatigability relationship; and evaluated the impacts of fatigue and fatigability on anxiety, depression, sleep disturbance, and endocrine symptoms. METHODS: A randomized controlled trial design was applied to an exercise program called BLESS (Better Life after cancer, Energy, Strength, and Support). The intervention included this 12-week exercise program and four follow-up contacts intended to promote exercise adherence over the following year. Participants were women aged 20 to 69 who had been diagnosed with stage I, II, or III breast cancer; had completed active treatment; and had moderate or higher fatigue. At the completion of the intervention, the survey responses of 40 BCS were evaluated using the chi-square test and multiple regression analysis. The Korean versions of the Revised Piper Fatigue Scale and Pittsburgh Fatigability Scale were used to measure fatigue and fatigability, respectively. RESULTS: There was no significant difference in fatigue or fatigability between the experimental and control groups at intervention completion. However, the control group showed a stronger association than the experimental group between fatigue and physical fatigability. In the control group, fatigue and fatigability were significantly associated with anxiety, depression, sleep disturbance, and endocrine symptoms. In the experimental group, only the cognitive/mood fatigue score and depression were significantly associated. Only endocrine symptoms influenced mental fatigability (B = − 0.185, P < 0.05), and only depression influenced cognitive/mood fatigue (B = 1.469, P < 0.05). CONCLUSIONS: Fatigue and fatigability showed different correlations with cancer-related symptoms after the exercise intervention. Future assessments of fatigability in intervention studies will allow measurement of the spectrum of patients’ abilities to overcome fatigue at various physical activity levels while capturing different aspects of cancer-related symptoms. TRIAL REGISTRATION: This study was retrospectively registered on Clinical Research Information Service (KCT0005763; date of registration: 31/12/2020).