Effects of E-Cigarettes & Tobacco on Heart Rate Variability Parameters, A Case-Control Study. Which One is Worse?

Background: This study aims to examine how heart rate variability (HRV) parameters, hemodynamic parameters and serum cotinine levels differ across the following groups: tobacco smokers, e-cigarette users and healthy non-smokers. This study explicitly examined a group of healthy people. Methods: Ninety healthy volunteers, aged between 18 and 45, were enrolled in the study (32 men and 58 women). Participants were divided into three groups of thirty each: e-cigarette users, traditional cigarette smokers and non-smokers. To examine the amount of tobacco exposure, serum cotinine levels were measured. Additionally, HRV data were examined in both the frequency and temporal domains. Statistical analyses were performed in Python 3.8 using the scikit-learn, pandas, and SciPy packages. Results: E-cigarette users had a noticeably longer smoking history than tobacco smokers (p=0.027). The baseline systolic blood pressure (SBP) and mean blood pressure (MBP) of the groups varied considerably (p=0.037 and p=0.021, respectively), with the non-smoker group exhibiting significantly higher SBP and MBP. For diastolic blood pressure (DBP), the change was borderline (p=0.073) but nearly significant. All HRV variables displayed standard deviation of normal-to-normal intervals (SDNN): -0.72 ms, root mean square of successive differences (RMSSD): -0.86 ms, proportion of consecutive RR intervals that is different by more than 50 ms (pNN50): -0.60% year and triangular interpolation of normal-to-normal intervals (TINN): -3.79 ms annually as age increased (all p ≤ 0.01). However, there were no significant differences in serum cotinine levels or HRV indices between e-cigarette users, non-smokers and traditional smokers (all p > 0.3). Conclusions: There were no discernible variations in cotinine levels or HRV indices among traditional cigarette smokers, e-cigarette users and non-smokers. The long-term effects of nicotine products require more research, including longitudinal designs, higher cohort sizes and other physiological and biochemical inflammatory indicators, such as endothelial function markers and cytokines.