Cigarette Smoking Trajectories of US Young Adults by Sex.

Introduction: While cigarette smoking is the leading cause of preventable morbidity and mortality in the United States (US), nearly one-fifth of young adults continue to smoke cigarettes, however, the prevalence remains higher in males than females.

Methods: The restricted panel data from the Monitoring the Future (MTF) study from 1976-2020 (n=24,293) was used. A group-based trajectory model (GBTM) was fit to the data for each sex (male/female), where groups were determined by cigarette smoking (yes/no) from the base year through the six biennial follow-up questionnaires. The analysis was then repeated overall and by decade.

Results: Four trajectory groups of cigarette smoking emerged for both sexes (male/female). Group 1 (60.8/62.0%) included participants with non-use of cigarettes. Group 2 (13.1/14.2%) captured individuals with moderate probability of use of cigarettes at baseline that decreased over time. Group 3 (7.1/5.5%) was the opposite of Group 2, where participants had low/moderate probability of cigarette smoking at baseline that increased over time. Group 4 (19.0/18.3%) captured individuals with high/moderate to high use of cigarettes throughout the study period. Overall and by decade analyses produced similar results.

Conclusions: Almost one quarter of the sample had increasing or high cigarette smoking, which suggests prioritizing interventions on recent high school graduates, regardless of sex, who begin with low cigarette smoking and increase over time and those with consistently high cigarette smoking. Future research will examine how different cigarette smoking trajectories relate to substance use and mental health outcomes.

Implications: This study provides a novel viewpoint on cigarette trajectory analysis among the adolescent and young adult population, stratified by sex. This stratification showed that regardless of sex, the same four distinct trajectory groups were present. This result was somewhat unanticipated as there are known discrepancies in both cigarette smoking initiation and cessation between the sexes.