Changes in heart rate variability during an eHealth behavior change intervention program in patients with cardiovascular disease

Background
Cardiovascular disease (CVD) risk is associated with health behaviors such as physical inactivity, dietary habits, and smoking. The autonomic nervous system plays a key role in this association. The present longitudinal study examines whether ECG-based indices of autonomic nervous system activity change during an eHealth-based behavior intervention program and assesses whether improvements in health behaviors are associated with increases in parasympathetic autonomic nervous system activity.

Methods
Data from the DoCHANGE-2 (https://clinicaltrials.gov/study/NCT03178305) eHealth-based behavior intervention study in patients with CVD were analyzed for participants with valid ECG recordings (N = 58, mean age = 58.9 [SD = 12.7] years, 21 % women). Heart rate variability (indexed as RMSSD) was calculated from home-recorded (40 s) ECGs over 5-day periods at baseline, 3, and 6 months. Health behaviors, clinical, and psychosocial information was obtained from questionnaires and medical records. Data were analyzed using linear mixed models and general linear models.

Results
Over the 6-month period, RMSSD decreased significantly, with the lowest values at six months (B = -19.336 [95 %CI −36.291; 2.381], p = 0.026). Health behaviors improved significantly during the active (0–3 months) intervention period (B = 13.360 [95 %CI 6.931 19.789], p < 0.001). Higher BMI (B = −0.369 [−0.739; 0.000]; p = 0.05) and older age (B = −0.404 [95 % CI −0.597; − 0.211]; p < 0.001) were associated with lower RMSSD across the three timepoints. No consistent associations were found between changes in health behaviors and changes in RMSSD.

Conclusion
This study shows that changes in HRV during an eHealth-based behavioral intervention were not associated with the observed improvements in health behaviors. These findings require replication in larger well-controlled investigations.