Contributors to Diminished Cardiorespiratory Fitness in Young Users of Electronic Cigarettes

Background: Cardiorespiratory fitness, an independent marker of cardiovascular health, represents the ability of respiratory, cardiovascular, and muscular systems to effciently deliver and utilize oxygen (O 2 ) during exercise. Recently, reduced cardiorespiratory fitness was identified in young and healthy, regular users of electronic (e-) cigarettes; however, its limiting factors are not established. Thus, the purpose of this study was to investigate the contributors to impaired cardiorespiratory fitness in young regular users of e-cigarettes. Methods: An evaluation of hemodynamics, chronotropic response, and oxygen utilization during exercise was completed in nineteen regular users of e-cigarettes (EU, age: 23±3 yr; e-cigarette usage 4±2 yr.) and sixteen demographically matched non-users (NU, age: 23±3 yr.). Hemodynamics were accessed via a non-invasive signal morphology impedance cardiography device, while chronotropic responses were measured as changes in peak heart rate (HR). Oxygen extraction ratio (difference in arterial and venous O 2 content) at baseline and peak exercise was also recorded. Fold changes from rest to peak exercise were assessed to provide insight into potential factors that limit cardiorespiratory fitness. Results: At peak exercise, users of e-cigarettes exhibited significantly higher chronotropic incompetence ( p=0.033) and lower ( p=0.047) peak HR than non-users, with no differences in other hemodynamic assessments. Significantly ( p=0.025) lower skeletal muscle O 2 extraction (EU=51±11 vs. NU=61±10%) was also observed in users of e-cigarettes during peak exercise. Fold changes in chronotropic (HR; p=0.915) and hemodynamic (cardiac output; p=0.279) responses were similar between both groups, while significant ( p=0.048) differences in oxygen extraction ratio were identified between the users of e-cigarettes (0.5±0.3 fold change) and non-users (0.8±0.3 fold change). Conclusions: Results from our study demonstrate that young, regular users of e-cigarettes exhibit abnormal chronotropic responses and impaired skeletal muscle oxygen utilization during exercise when compared to non-users, suggesting reduced cardiovascular and muscle health. Overall, our findings contribute to the growing body of evidence that supports the negative effects of regular e-cigarette use on young individuals. Supported in part by a Rapid Response Project NIDA/FDA (PRM). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.