Vascular and Cardiac Autonomic Function in Electronic Cigarette Users

Phillips, Olivia Louise (2025) Vascular and Cardiac Autonomic Function in Electronic Cigarette Users. Masters by Research thesis (MSc), Manchester Metropolitan University.

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Abstract

Introduction: Tobacco cigarette (TC) smoking is a significant risk factor for cardiovascular morbidity and mortality, primarily due to its detrimental effects on vascular and cardiac autonomic function. Electronic cigarettes (EC) were introduced as a potential smoking cessation aid. However, their popularity in novice users has surged to epidemic levels. Acute exposure to ECs has been shown to increase circulating markers of oxidative stress and inflammation. However, the chronic effects of exclusive EC use on cardiovascular function remain unclear. Methodology: Vascular and endothelial function were assessed by measuring carotid to radial artery pulse wave velocity (PWV) and brachial artery flow mediated dilation (FMD) respectively in young (18-38 years) healthy controls (HC; n=48), EC users ( n=39) with no history of tobacco use and TC smokers (n=38) with no history of EC use. Cardiac autonomic function was assessed by measuring heart rate variability (HRV) and spontaneous baroreceptor reflex sensitivity (BRS) in young (19-28) years HC (n=25), EC users (n=16), and TC smokers (n=15). Venous blood samples were acquired to assess serum / plasma markers of inflammation and oxidative stress. Results: FMD (35% lower in EC and TC compared to HC, p=0.001), HRV (29% and 21% lower in EC and TC compared to HC, p<0.001) and spontaneous BRS were similarly lower in TC and EC users compared to HC; while PWV was similarly greater in TC (42%) and EC (33%) compared to HC (p<0.001). Cotinine (525% and 675% greater in EC and TC compared to HC, p<0.001), interleukin-6 (IL-6) (56% and 41% greater in EC and TC compared to HC, p=0.003), tumour necrosis factor-alpha (TNF-ɑ) (83% and 48% greater in EC and TC compared to HC, p=0.004), and malondialdehyde (MDA) levels (33% and 49% greater in EC and TC compared to HC, p<0.001) were similarly raised in TC and EC users compared to HC. Conclusion: This study reveals that chronic lone use of ECs produces similar impairments in endothelial and cardiac autonomic function as chronic lone TC use. Considering endothelial dysfunction and autonomic dysfunction are independently linked with raised future risk of adverse cardiovascular events, these findings suggest that ECs are not a safe alternative to TCs for nicotine addiction, emphasising the need for health polices addressing EC use and promotion.