Trends in the Age of Cigarette Smoking Initiation Among Young Adults in the US From 2002 to 2018

IMPORTANCE Success in reducing the prevalence of adolescent smoking could reflect complete prevention of smoking initiation or a shift in the age of cigarette smoking initiation from adolescence into early adulthood. OBJECTIVE To assess trends in early adult (ages 18-23 years) vs adolescent (age <18 years) cigarette smoking initiation and transition to daily cigarette smoking from 2002 to 2018. DESIGN, SETTING, AND PARTICIPANTS Ages at initiation of smoking and the transition to daily smokingwere ascertained from the National Survey on Drug Use and Health (2002-2018), an annual, population-based, repeated cross-sectional study representative of the US population. This crosssectional analysis was restricted to young adults who completed the survey at ages 22 to 23 years during survey years 2002 to 2018 to limit potential age-related recall bias. Retrospectively collected age of cigarette smoking initiation was assessed among ever cigarette smokers; age of transition to daily smoking was assessed among ever daily cigarette smokers. Data analysis was performed from June 2019 to July 2020. EXPOSURES Calendar year of survey (2002 to 2018). MAIN OUTCOMES AND MEASURES The main outcomes were population-weighted cigarette smoking prevalence and cigarette smoking initiation and transition to daily smoking in adolescence (age <18 years) vs early adulthood (ages 18-23 years). RESULTS Among 71 756 young adults aged 22 to 23 years (38 226 women [50.5%]), ever cigarette smoking prevalence decreased from a population-weighted estimate of 74.6%(95% CI, 73.1%-75.9%) in 2002 to 51.4%(95% CI, 49.3%-53.5%) in 2018 (P <.001). Daily smoking prevalence rates similarly decreased from 41.1%(95% CI, 39.1%-43.1%) in 2002 to 20.2%(95% CI, 18.6%-21.8%) in 2018 (P <.001). However, among 48 015 ever smokers, the proportion initiating smoking in early adulthood (ages 18-23 years) increased over this time, from 20.6%(95% CI, 18.5%-22.8%) in 2002 to 42.6%(95% CI, 39.6%-45.7%) in 2018 (P <.001). Similarly, among 24 490 daily cigarette smokers, the proportion who transitioned to daily smoking in early adulthood increased from 38.7% (95% CI, 35.9%-41.6%) in 2002 to 55.9% (95% CI, 52.0%-59.8%) in 2018 (P <.001). CONCLUSIONS AND RELEVANCE A substantial proportion of beginning smokers and most new daily smokers are now young adults, reflecting a shift from adolescence to early adulthood, a population segment once considered beyond the critical risk period for cigarette smoking onset. Expanding the long-standing emphasis on adolescent surveillance and prevention in adolescence to include the young adult population is warranted.