Changes in cardiovascular disease risk, lung function and other clinical health outcomes when people who smoke use e-cigarettes to reduce cigarette smoking: an exploratory analysis from a randomised placebo-controlled trial

Abstract

Objectives: To examine changes in cardiovascular disease (CVD) risk factors, lung function and clinical laboratory markers among people who smoke who used e-cigarettes to reduce their cigarette smoking.

Design: Four-arm, parallel-group, double-blind, randomised placebo-controlled trial.

Setting: Two sites-Virginia Commonwealth University (Richmond, Virginia, USA) and Penn State University, College of Medicine (Hershey, Pennsylvania, USA).

Participants: Adults (n=520) aged 21-65 years who smoked at least 10 cigarettes per day, had an expired-air carbon monoxide reading of >9 parts per million at baseline and were interested in reducing their cigarette consumption.

Interventions: E-cigarettes with 0, 8 or 36 mg/mL nicotine liquid concentration or a cigarette substitute.

Primary outcome measures: CVD risk factors (blood lipids, C-reactive protein, blood pressure, heart rate, waist-to-hip ratio, body mass index and INTERHEART risk score), lung function (spirometry indices, and pulmonary symptoms and functional state using the Clinical Chronic Obstructive Pulmonary Disorder Questionnaire), and other clinical laboratory markers (complete blood count and complete metabolic panel).

Results: At 6 months, the use of nicotine e-cigarettes caused no significant between-group differences for most measures. However, participants randomised to the 36 mg/mL e-cigarette condition had significantly higher levels of high-density lipoprotein (HDL) (p=0.003 unadjusted, p=0.002 adjusted) and lower levels of low-density lipoprotein (LDL) (p=0.044 adjusted) and cholesterol/HDL ratio (p=0.034 unadjusted, p=0.026 adjusted) compared with the cigarette substitute condition. Also, those in the 36 mg/mL e-cigarette condition had higher HDL levels than those in the 0 mg/mL condition (p=0.016 unadjusted, p=0.019 adjusted).

Conclusions: Participants randomised to the highest nicotine e-cigarette condition showed modest improvements in some measures of blood lipids (eg, increased HDL, and reduced LDL and cholesterol/HDL ratio) as compared with a non-aerosol cigarette substitute among individuals attempting to reduce their cigarette smoking. Future studies of e-cigarettes for smoking cessation would benefit from including these measures to further explore the results found in this study.

Trial registration number: NCT02342795.

Keywords: PUBLIC HEALTH; Randomized Controlled Trial; Tobacco Use.

Figure 1. (A–D) Unadjusted mean of FEV₁ (A), HDL (B), cholesterol/HDL ratio (C) and LDL (D) at baseline and at 6 months follow-up across randomised conditions. *A significant difference between the 36 mg/mL e-cigarette condition relative to the cigarette substitute condition in unadjusted intention-to-treat analysis at 6 months (p<0.05). #A significant difference between the 36 mg/mL e-cigarette condition relative to the 0 mg/mL e-cigarette condition in unadjusted intention-to-treat analysis at 6 months (p<0.05). FEV1, forced expiratory volume in 1 s; HDL, high-density lipoprotein; LDL, low-density lipoprotein.