A new study conducted by the University of Louisville (UofL) has found that certain types of e-cigarettes with higher nicotine levels can be more harmful to the heart, increasing the risk of irregular heartbeat or heart arrhythmias. The study challenges the popular belief that nicotine in e-cigarettes is relatively harmless, suggesting that the type and concentration of nicotine can modify the adverse cardiovascular effects of e-cigarette aerosols.
The study, which was published in Nicotine and Tobacco Research, involved testing the effects of e-cigarettes with different types and doses of nicotine on animal models. The research compared heart rate and heart rate variability in mice exposed to vape aerosols containing various types of nicotine, including freebase nicotine used in older types of e-cigarettes, nicotine salts found in Juul and other pod-based e-cigarettes, and racemic freebase nicotine simulating synthetic nicotine. The study also included nicotine-free e-cigarette aerosols and air for comparison. Increasing concentrations of nicotine were delivered over time, ranging from 1% to 2.5% to 5%.
The severity of the arrhythmias increased with higher concentrations of nicotine. These findings suggest that nicotine is harmful to the heart and challenge the notion that nicotine alone is harmless. The study also found that higher levels of nicotine salts increased sympathetic nervous system activity, which is associated with the fight-or-flight response. This occurs by stimulating the same receptor that is inhibited by beta-blockers, medications prescribed to treat cardiac arrhythmias.
According to Alex Carll, assistant professor in UofL’s Department of Physiology and the lead researcher of the study, the nicotine in e-cigarettes causes irregular heartbeats in a dose-dependent manner by stimulating the same receptor that many heart medications aim to inhibit. The study concludes that the inhalation of e-cigarette aerosols from nicotine-salt-containing e-liquids could increase cardiovascular risks by inducing sympathetic dominance and cardiac arrhythmias.
This research is part of a larger body of evidence on the potential toxicity and health impacts of e-cigarettes. The American Heart Association Tobacco Regulation and Addiction Center, with UofL as the flagship institute, has reported on the potential health risks associated with e-cigarettes. Previous research by the UofL team found that exposure to e-cigarette aerosols containing certain flavors or solvent vehicles caused ventricular arrhythmias and other heart irregularities, even without nicotine. This suggests that the arrhythmias may not be solely attributed to nicotine but may also be influenced by the flavors and solvents used in e-cigarettes.
The researchers suggest that if the results of this study are confirmed in humans, regulatory measures should be considered to mitigate the public health risks of vaping. These measures could include regulating nicotine salts through minimum pH standards or imposing limits on acid additives in e-liquids. In the meantime, the study suggests that users may reduce potential harm by opting for e-cigarettes with freebase nicotine instead of nicotine salts or by choosing e-cigarettes with lower nicotine content.
1. Source: Coherent Market Insights, Public sources, Desk research
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