Introduction:
Breast cancer remains the most commonly type of cancer. Heart rate variability (HRV), a clinical indicator of autonomic dysfunction and premature mortality, has been found to be impaired in breast cancer survivors immediately after treatment and in the last stages of metastasis. Physical activity and fitness represent relevant health markers that might prevent some of the side effects following breast cancer treatment, so it would be of clinical interest assessing potential differences with healthy controls.
Hypothesis:
Compared to healthy women, breast cancer survivors are expected to show impaired HRV-derived parameters, as well as lower physical activity and fitness.
Methods:
This cross-sectional study included 20 women that survived breast cancer (post-operative period >2 years) and 20 healthy women controls, matched by age and BMI. Fitness evaluations included the modified Ruffier-Dixon test and handgrip strength. Moderate-to-vigorous physical activity (MVPA) was assessed through a self-reported questionnaire. Short-term HRV was measured using 5-minutes recording and were analyzed with Kubios Premium. Sample size was determined for two-tailed tests, statistical power of 0.8, effect size >0.7, and significance level of p<0.05. Between-groups differences were examined using Mann–Whitney U test and Student’s t-test, for normally and not-normally distributed variables, respectively.
Results:
Concerning HRV parameters, breast cancer survivors presented lower Very Low Frequency and Low Frequency, and higher Low Frequency/High Frequency ratio (all
p
<0.001), compared to controls. No statistically significant differences were observed in MVPA time (
p
=0.48) or estimated VO
2max
(
p
=0.24), although handgrip strength was decreased in cancer survivors (
p
=0.02).
Conclusions:
A cardiovascular imbalance in breast cancer survivors may be suggested in comparison to healthy age- and BMI-matched controls, as evidenced by reduced HRV after >2 years of post-operative treatment. In contrast, there were no differences in weekly MVPA or VO
2max
between groups, although muscular strength could still be affected. These results need to be contrasted by future long-term prospective research.
Associations between lifestyle factors and breast cancer in healthy women and breast cancer survivors and need for ehealth support
