Effects of E-cigarette and tobacco use on heart rate variability: a case-control study

This study aims to examine heart rate variability (HRV) parameters, hemodynamic parameters, and serum cotinine levels difference across the following groups: tobacco smokers, e-cigarette users and non-smokers. This study explicitly examined healthy people. Ninety healthy volunteers, aged between 18 and 45, were enrolled in the study. Participants were divided into three groups of thirty each: e-cigarette users, tobacco smokers and non-smokers. HRV data were examined in both the frequency and temporal domains. Additionally, statistical analyses were performed in Python 3.8 using the scikit-learn, pandas, and SciPy packages. Tobacco smokers had a significantly longer smoking history than e-cigarette users (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): -0.73 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): -4.07 ms annually as age increased (all p ≤ 0.01). No statistically significant differences in cotinine levels or HRV indices were observed among tobacco smokers, e-cigarette users and non-smokers in this exploratory study. 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.