Risk factors for adolescent smoking uptake: an analysis of prospective data from the Millennium Cohort Study

Preventing smoking uptake among adolescents is essential to achieve a smoke-free generation. The aim of this study was to assess risk factors for smoking in late adolescence and smoking uptake between early and late adolescence, using data from the Millennium Cohort Study. We also present estimates of numbers of smokers and smoking uptake.Adolescents aged 14-17 years were included in the analysis. In separate logistic regression models, we assessed associations between age, sex, ethnicity, household income, country of residence, current smoking of a caregiver, current smoking of peers and use of social media, and regular smoking (defined as smoking at least one cigarette per week) at the age of 17 years and smoking uptake between the ages of 14 and 17 years (defined as being a never-smoker at the age of 14 years and a regular smoker at the age of 17 years). We also estimated numbers of regular smoking and smoking uptake using the Office for National Statistics 2018-19 population estimates.Data from 8944 adolescents aged 14-17 years with smoking data available were included, 948 (10·6%) of which were regular tobacco smokers at the age of 17 years. 488 (51·5%) of these 948 started smoking between the ages of 14 years and 17 years. Smoking uptake was more common among adolescents reporting caregiver smoking (162 [13·6%] of 1188 vs 324 [5·0%] of 6538 with non-smoking caregivers; p<0·0001); peers smoking (223 [12·6%] of 1764 vs 229 [4·3%] of 5350 without smoking peers; p<0·0001), and those reporting higher (at least 5 h/weekday) social media use (115 [9·8%] of 1176 vs 120 [4·1%] of 2947 with lower [less than 1 h/weekday] social media use; p=0·0059), among 7786 adolescents who did not smoke at age 14. We estimated that 164 313 (95% CI 146 815-181 811) adolescents were regular smokers by the age of 17 years, of whom 101 715 (85 994-117 435) took up the habit between the age of 14 years and 17 years.Our findings are a reminder of the transmissibility of the smoking epidemic. Although we only assessed social media use, not actual exposure to online tobacco advertising, our findings strengthen calls for awareness of the changing landscape of tobacco advertising.Cancer Research UK (grant reference PPRCTAGPJT\100005) and the UK National Institute for Health and Care Research School for Public Health Research. The funders had no role in the writing of the manuscript or the decision to submit for publication.