Objectives

The aim was to identify predictors of electronic cigarette (e-cigarette) use among teenagers.

Design and setting

A prospective population-based cohort study of schoolchildren in northern Sweden.

Participants

In 2006, a cohort study about asthma and allergic diseases among schoolchildren started within the Obstructive Lung Disease in Northern Sweden studies. The study sample (n=2185) was recruited at age 7–8 years, and participated in questionnaire surveys at age 14–15 and 19 years. The questionnaire included questions about respiratory symptoms, living conditions, upper secondary education, physical activity, diet, health-related quality of life, parental smoking and parental occupation. Questions about tobacco use were included at age 14–15 and 19 years.

Primary outcome

E-cigarette use at age 19 years.

Results

At age 19 years, 21.4% had ever tried e-cigarettes and 4.2% were current users. Among those who were daily tobacco smokers at age 14–15 years, 60.9% had tried e-cigarettes at age 19 years compared with 19.1% of never-smokers and 34.0% of occasional smokers (p<0.001). Among those who had tried e-cigarettes, 28.1% were never smokers both at age 14–15 and 19 years, and 14.4% were never smokers among the current e-cigarette users. In unadjusted analyses, e-cigarette use was associated with daily smoking, use of snus and having a smoking father at age 14–15 years, as well as with attending vocational education, physical inactivity and unhealthy diet. In adjusted analyses, current e-cigarette use was associated with daily tobacco smoking at age 14–15 years (OR 6.27; 95% CI 3.12 to 12.58), attending a vocational art programme (OR 2.22; 95% CI 1.04 to 4.77) and inversely associated with eating a healthy diet (OR 0.74; 95% CI 0.59 to 0.92).

Conclusions

E-cigarette use was associated with personal and parental tobacco use, as well as with physical inactivity, unhealthy diet and attending vocational upper secondary education. Importantly, almost one-third of those who had tried e-cigarettes at age 19 years had never been tobacco smokers.