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.