Abstract
Background and aims
Most studies in English‐speaking countries have found a positive association between e‐cigarette experimentation and subsequent daily tobacco smoking among adolescents. However, this result may not be valid in other cultural contexts; in addition, few studies have assessed whether this association varies with the subject’s age at the time of e‐cigarette experimentation. This study aimed to estimate the association between experimenting first with e‐cigarette (rather than tobacco) and subsequent daily smoking according to age at the time of experimentation.
Design
Secondary analysis; risk‐ratios (RRs) computed using modified Poisson regressions with inverse probability weighting.
Setting
A cross‐sectional nationwide representative survey performed in 2017 in France.
Participants
French adolescents (n=24,111), aged 17 to 18.5 years, who had previously experimented with either e‐cigarettes or tobacco.
Measures
Exposure was defined as the experimentation with e‐cigarettes first (whether or not followed by experimentation with tobacco); the outcome as daily tobacco smoking at the time of data collection. Gender, age, literacy, socioeconomic status, pre‐exposure repeat school years and experimentation with 12 other licit and illicit drugs were adjusted for. Uncertainties about the sequence of events defining exposure were handled by the definition of three patterns of exposure, to avoid a misclassification bias.
Findings
Exposure reduced the risk of transition to daily smoking: RR=0.58, 95%CI=[0.54, 0.62]. This effect increased in linear manner with age at exposure (RR=0.87, 95%CI=[0.78; 0.98] for 1 year, p<0.001): from RR=1.30 95%CI=[1.09; 1.54] at age 9 to RR=0.38, 95%CI=[0.32; 0.45] at age 17.
Conclusions
Experimenting with e‐cigarettes first (as opposed to tobacco first) appears to be associated with a reduction in the risk of daily tobacco smoking among French adolescent at ages 17‐18.5, but this risk varies negatively with age at experimentation, and early e‐cigarette experimenters are at higher risk.