Biomarkers of potential harm in people switching from smoking tobacco to exclusive e-cigarette use, dual use or abstinence: secondary analysis of Cochrane systematic review of trials of e-cigarettes for smoking cessation.

Aims: This study aims to compare biomarkers of potential harm between people switching
from smoking combustible cigarettes (CC) completely to electronic cigarettes (EC),
continuing to smoke CC, using both EC and CC (dual users) and using neither
(abstainers), based on behaviour during EC intervention studies.
Design: Secondary analysis following systematic review, incorporating inverse variance
random-effects meta-analysis and effect direction plots.
Setting: This study was conducted in Greece, Italy, Poland, the United Kingdom and the
United States.
Participants: A total of 1299 adults smoking CC (nine studies) and provided EC.
Measurements: Measurements were conducted using carbon monoxide (CO) and 26
other biomarkers.
Findings: In pooled analyses, exhaled CO (eCO) was lower in EC versus EC + CC [mean
difference (MD) = −4.40 parts per million (p.p.m.), 95% confidence interval (CI) = −12.04
to 3.24, two studies] and CC (MD = −9.57 p.p.m., 95% CI = −17.30 to −1.83, three studies).
eCO was lower in dual users versus CC only (MD = −1.91 p.p.m., 95% CI = −3.38 to
−0.45, two studies). Magnitude rather than direction of effect drove substantial statistical
heterogeneity. Effect direction plots were used for other biomarkers. Comparing EC
with CC, 12 of 13 biomarkers were significantly lower in EC users, with no difference for
the 13th. Comparing EC with dual users, 12 of the 25 biomarkers were lower for EC, and
five were lower for dual use. For the remaining eight measures, single studies did not
detect statistically significant differences, or the multiple studies contributing to the outcome
had inconsistent results. Only one study provided data comparing dual use with
CC; of the 13 biomarkers measured, 12 were significantly lower in the dual use group,
with no statistically significant difference detected for the 13th. Only one study provided
data on abstainers.

hartmann-Boyce J, Butler aR, Theodoulou a, et al. Biomarkers of potential harm in people switching from smoking tobacco to exclusive e-cigarette use, dual use or abstinence: secondary analysis of Cochrane systematic review of trials of e-cigarettes for smoking cessation. addiction (abingdon, England). 2023;118(3):539-545. doi:10.1111/add.16063