Electronic cigarettes, nicotine use trends and use initiation ages among US adolescents from 1999 to 2018.

Electronic cigarettes may have offset conventional smoking among US adolescents between 2010 and 2018 by maintaining the total nicotine use prevalence and diverting them from more harmful conventional smoking. Additionally, electronic cigarette users appear to initiate at older ages relative to conventional smokers, which is associated with lower risk.