| Summary: | <p><strong>Aims</p></strong>
To determine patterns of e-cigarette flavour use (sweet, tobacco, menthol/mint) in interventional
studies of e-cigarettes for stopping smoking, and to estimate associations between flavours and
smoking/vaping outcomes.
<p><strong>Methods</p></strong>
Update of secondary data analyses, including meta-analyses subgrouped by flavour provision and
narrative syntheses, incorporating data from January 2004 to February 2024. Eligible studies were
identified from a Cochrane review. Studies provided adults who smoked cigarettes with nicotinecontaining e-cigarettes for smoking cessation and provided data on e-cigarette e-liquid flavour use.
Outcomes included participants’ flavour use measured at any time, plus smoking abstinence,
abstinence from all tobacco or commercial nicotine products, and allocated product use at 6 months
or longer, reported as risk ratios with 95% confidence intervals. We assessed risk of bias using the
Cochrane Risk of Bias 1 tool.
<p><strong>Results</p></strong>
We included 25 studies (n=16,748); 21 contributed to subgroup meta-analyses and 18 provided
flavour choices. We judged 15 studies at high, seven at low, and three at unclear risk of bias. In
studies where participants had a choice of flavours, some switching between flavours occurred (five
studies). A preference for sweet (including fruit) flavours over tobacco and menthol was indicated (in
6 of 11 studies); however, there were differences across studies. Subgroup meta-analyses showed
no clear associations between e-liquid flavours provided and smoking cessation or study product
use. One included study randomised participants to two different flavour conditions and found
similar cessation rates and long-term e-cigarette use between arms at 12 months.
<p><strong>Conclusions</p></strong>
Some people using e-cigarettes to quit smoking switch between e-cigarette flavours during a quit
attempt. Sweet flavours may be preferred overall, but this may differ depending on context. Based
on intervention studies there is no clear association between the use of e-cigarette flavours and
smoking cessation or longer-term e-cigarette use, possibly due to a paucity of data.
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