A fifth of teenagers who smoked e-cigarettes only were smoking tobacco a year later, compared with only 6% of those who did not smoke either initially, a study from the United States has found.

A longitudinal observational study, involving 2,338 students from six high schools in Hawaii, was carried out. The students aged 14-16, mean 14.7 years, were questioned about e-cigarette use and other smoking behaviour at baseline in 2013 and again a year later.

All data analyses were controlled for demographic and psychosocial variables that could be linked to e-cigarette use and to smoking.

Almost all of those interviewed in 2013 (96%) had heard of e-cigarettes, and around two thirds (68%) considered them healthier than smoking tobacco.

Just under a third of the students (31%) had used e-cigarettes by 2013, and this increased to 38% by 2014. Significantly fewer students (15%) had smoked at least one cigarette in 2013, rising to around one in five (21%) by 2014.

Of the original e-cigarette use only group, 20% had started tobacco smoking by 2014. Of those who smoked neither e-cigarettes nor tobacco at baseline, 10% had started smoking e-cigarettes, 2% cigarettes and 4% both by 2014.

Students with higher levels of family support and education were less likely to make the transition from not using either e-cigarettes or tobacco to use of both by the time of the second interview.

E-cigarette use among cigarette smokers at baseline was not linked to any reduction in tobacco smoking frequency by the second interview.

The clear conclusion from this study is that adolescents who use e-cigarettes are more likely to start smoking cigarettes than those who do not use e-cigarettes.

The authors go on to suggest that policies which restrict adolescents’ access to e-cigarettes may be justifiable from a public health perspective.

Dr Jez Thompson

Wills TA, Knight R, Sargent JD et al. Longitudinal study of e-cigarette use and onset of cigarette smoking among high school students in Hawaii. Tob Control 2016;0:1–6. doi:10.1136/tobaccocontrol-2015-052705