Objective:
Smartphones are considered a double-edged sword in the tobacco control field. Ideally, the device can be used for efficiently delivering prevention and cessation programs. However, there are also concerns adolescents may be receiving pro-smoking messages via smartphones. This study aimed to examine the association between time spent on smartphones and exposure to online tobacco advertisements among youths.

Methods:
The 13th (2017) Korean Youth Risk Behavior Survey, a nationally representative data of South Korean adolescents, were used. Along with the exposure to online tobacco advertisements during the past 30 days, smartphone use, and average time spent on smartphones per day were measured. Time spent were defined in quantiles. Multiple logistic regression analyses were performed, adjusting for sex, grade and perceived household wealth.

Results:
Among 62,276 adolescents, 87.7% used smartphones during the past 30 days. The average time spent on smartphones per day was 266.8 minutes (4.4 hours). 39.6% of smartphone non-users were exposed to online tobacco advertisements, whereas 44.0% of users were exposed. More time spent on smartphones was associated with more exposure to online advertisements. Odds ratio estimates (reference=smartphone non-use) were as follows: Q1 (1.07, 95% CI=1.01-1.13), Q2 (1.20, 95% CI=1.13-1.27), Q3 (1.24, 95% CI=1.17-1.31) and Q4 (1.33, 95% CI=1.26-1.41).

Conclusions:
Our results indicate a dose-response relationship between the time spent on smartphones and exposure to online tobacco advertisements. This implies tobacco advertisements are accessible through smartphones among youths. Tobacco advertisements on the internet is a violation to the article 13 of the WHO Framework Convention Tobacco Control. Further research and control measures are required to tackle online advertisements.