The relationship between heart rate variability and TNM stage, co-morbidity, systemic inflammation and survival in patients with primary operable colorectal cancer

High vagal nerve activity, reliability measured by HRV, is considered protective in cancer, reducing oxidative stress, inflammation and opposing sympathetic nerve activity. The present monocentric study examines the relationship between HRV, TNM stage, co-morbidity, systemic inflammation and survival in patients who underwent potentially curative resections for colorectal cancer (CRC). Time-domain HRV measures, Standard Deviation of NN-intervals (SDNN) and Root Mean Square of Successive Differences (RMSSD), were examined as categorical (median) and continuous variables. Systemic inflammation was determined using systemic inflammatory grade (SIG) and co-morbidity using ASA. The primary end point was overall survival (OS) and was analysed using Cox regression. There were 439 patients included in the study and the median follow-up was 78 months. Forty-nine percent (n = 217) and 48% (n = 213) of patients were categorised as having low SDNN (< 24 ms) and RMSSD (< 29.8 ms), respectively. On univariate analysis, SDNN was not significantly associated with TNM stage (p = 0.830), ASA (p = 0.598) or SIG (p = 0.898). RMSSD was not significantly associated with TNM stage (p = 0.267), ASA (p = 0.294) or SIG (p = 0.951). Neither SDNN or RMSSD, categorical or continuous, were significantly associated with OS. In conclusion, neither SDNN or RMSSD were associated with TNM stage, ASA, SIG or survival in patients undergoing potentially curative surgery for CRC.