Introduction:
We investigated various favourable perceptions of ecigarettes (ECs) relative to cigarettes in adolescents and their associations with EC use intention among never EC users.

Material and Methods:
In 2014/15, 40202 secondary 1-6 (US grade 7-12) students (51.5% boys, mean age 14.9±1.8 years) in Hong Kong were surveyed. The study factors were 13 perceived advantages of ECs over cigarettes (agree vs disagree). Intention to use ECs (outcome) referred to the lack of a firm decision not to use ECs in the next 12 months or when offered by a good friend. Weighted prevalence of the favourable perceptions of ECs in all students was calculated. Cox regression yielded prevalence ratios of intention to use ECs for each favourable perception in never EC users, excluding those unaware of ECs. Socio-demographic characteristics, cigarette smoking and school clustering effect were adjusted for.

Results:
Of all students (n=40202), 47.2% perceived any advantages of ECs over cigarettes, with “less likely to cause accidents”, “less health harms on users” and “less health harms on others” being most common. In never EC users (n=24663), each favourable perception was associated with an intention to use ECs, the strongest were “more attractive”, “better accepted by parents” and “better accepted by schools”.

Conclusions:
Favourable perceptions of ECs were strongly associated with intention to use ECs in adolescents who had never used ECs. Our findings support interventions to raise public awareness of the potential harms of ECs and increase parental and school disapproval of adolescent EC use, and effective regulations to prevent adolescent EC use.

Funding:
The Food and Health Bureau, Hong Kong SAR Government, China