Vascular and Cardiovascular Outcomes of Smoking Cessation and Switching to Electronic Cigarette Use: Protocol for a Systematic Review of Prospective Studies.

Abstract

Background: Despite the well-documented adverse health effects of tobacco smoking, it remains prevalent worldwide. Chronic tobacco smoking is associated with significant cardiovascular effects, including an increased risk of cardiovascular disease and vascular dysfunction. In recent years, the use of electronic cigarettes (ECs) has increased, with many former tobacco cigarette smokers switching to ECs to aid in smoking cessation. To date, no systematic review has synthesized prospective evidence on key vascular and cardiovascular outcomes among adult smokers who quit or switch to ECs, with the specific aim of identifying early and clinically meaningful indicators of vascular recovery.

Objective: This systematic review aims to summarize the current prospective studies on the vascular effects of switching to exclusive EC use and the overall effects of smoking cessation on regular tobacco cigarette smokers. The review will focus, in particular, on early indicators of vascular improvement, such as measures of vascular function, including arterial stiffness and endothelial function, as well as on heart rate, blood pressure, nonfatal myocardial infarction, nonfatal stroke, sudden cardiovascular death, and acute heart failure.

Methods: The review will be reported following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A comprehensive search was performed in PubMed and Scopus on January 12, 2025, without restrictions on the publication date. Studies will be included if they focus on cardiovascular outcomes, with study designs, including clinical trials (randomized controlled trials, observational studies), prospective cohort studies, and case-control studies. Studies involving regular smokers, aged 18 years and older, and those reporting on smoking cessation or switching to ECs will be considered. Data will be extracted using a standardized form and synthesized qualitatively. Risk of bias will be assessed using Joanna Briggs Institute's critical appraisal tools, with results informing sensitivity analyses and interpretation.

Results: As of January 2025, the preliminary search retrieved 1479 records across PubMed and Scopus. At the time of this protocol's publication, the first manuscript on vascular function outcomes was completed in July 2025 and is currently under peer review. Each subsequent review will include an updated search before completion.

Conclusions: This review will provide a comprehensive landscape of current literature on the long-term vascular effects of smoking cessation and switching to exclusive EC use. The findings will help identify early indicators of vascular damage reversal, gaps in the current evidence base, and inform future research directions. By disseminating the results through peer-reviewed journals, conferences, and digital platforms, the review aims to enhance the understanding of smoking cessation's impact on vascular health and support public health efforts in reducing tobacco-related harm.

Trial registration: PROSPERO CRD420251016878; https://www.crd.york.ac.uk/PROSPERO/view/CRD420251016878.

International registered report identifier (irrid): PRR1-10.2196/74949.