Association Between Heart Rate Variability and Fatigue in Breast Cancer Survivors: A Cross-Sectional Study

This is the authors' abstract. We don't add key points for this paper.

Breast cancer and its treatments may disrupt autonomic nervous system regulation, reduce physiological adaptability, and induce symptoms such as cancer-related fatigue (CRF), one of the most prevalent, persistent and debilitating conditions in breast cancer survivors (BCS). However, the underlying biological mechanisms of CRF remain unclear. Heart rate variability (HRV) is a non-invasive biomarker of autonomic function, yet evidence linking HRV to CRF in BCS is limited. This study aimed to explore HRV after treatment completion and to examine its potential associations with CRF. Short-term HRV recordings were obtained in supine and standing positions using a validated chest strap heart rate monitor (Polar V800 with the standard H10 chest strap). Time-domain (i.e., SDNN and RMSSD) and frequency-domain (i.e., LF, HF, and LF/HF ratio) indices were derived. Fatigue was measured using PERFORM questionnaire. Bivariate linear regression models were used to examine associations between HRV indices and fatigue scores. Seventy-six BCS (mean age 51.1 ± 7.7 SD years), were evaluated. Mean PERFORM scores were 46.78 ± 12.08. Overall, HRV values were lower than normative data in healthy adults. The LF/HF ratio was elevated, suggesting sympathetic predominance. Mean RR intervals were shorter than in healthy adults, consistent with increased sympathetic tone. No statistically significant association between HRV and fatigue was found. BCS showed reduced HRV compared with normative values, but HRV was not associated with fatigue. This may reflect moderate fatigue levels, limited representation of older women and those on hormonal therapy, and other confounders; larger studies with standardized HRV protocols are needed.