Can Physical Exercise Attenuate Heart Rate Variability Decline Produced By Cancer?

Abstract

As cancer therapies have evolved, survival rates have increased, yet side-effects still exist. Cardiotoxicity and neurotoxicity have negative effects on the autonomic nervous system and create cardiovascular dysfunction. Heart rate variability (HRV), a marker of autonomic modulation, negatively decreases with cancer, and is associated with fatigue, depression, and mortality. Exercise appears to attenuate the decline in HRV. PURPOSE: This review analyzes the effects of exercise programs on HRV of cancer patients and survivors. METHODS: PRISMA guidelines were followed by searching Web of Science articles and PubMed databases. The quality of the articles was assessed by PEDro scale. Statistical procedures used Revman 5.3. RESULTS: Six studies fulfilled the inclusion/exclusion criteria and included 272 participants, 30 to 75 years old. Exercise programs had a mean length of 10.4 wks, a frequency of 3.1 d/wk, and a mean duration of 78 min/session. In the time domain HRV measures, exercise increased in Standard deviation of NN intervals (p < 0.00001; MD = 12.79 ms [95% CI = 9.03 to 16.55]) and decreased Root mean square of successive RR interval differences (p = 0.002; MD = 13.08 ms [95% CI = 4.90 to 21.27]) compared to controls. Frequency domain data reveal that significant differences between control and exercise groups could be reached in low-frequency (absolute power: p < 0.0001; SMD = 0.97 [95% CI = 0.61 to 1.34]; relative power: p = 0.04; MD = -7.70 [95%CI = -15.4 to -0.36]) high-frequency (absolute power: p = 0.001, SMD = 1.49 [95% CI = 0.32 to 2.66]; relative power: p = 0.04, MD = 8.00 nu [95% CI = 0.20 to 15.80]) and HF/LF ratio (p = 0.007; MD = -0.32 [95% CI = -0.55 to -0.09). CONCLUSIONS: Exercise programs can lead to positive effects on HRV of cancer patients and survivors, with more positive changes realized with resistance and endurance workouts. However, the overall small sample size studying exercise and HRV in cancer patients warrants further study to confirm these results.