Trends in E-Cigarette Use by Age Group and Combustible Cigarette Smoking Histories, U.S. Adults, 2014-2018.

Introduction: The trends in e-cigarette prevalence and population count of users according to cigarette smoking histories are unknown. These data are needed to inform public health actions against a rapidly changing U.S. e-cigarette market.

Methods: Data collected between 2014 and 2018 (analyzed in 2020) from cross-sectional, nationally representative National Health Interview Surveys were used to estimate current e-cigarette prevalence, adjusted prevalence differences (percentage points), and population counts of users. Analyses were stratified by age group (younger, 18-29 years, n=25,445; middle age, 30-49 years, n=47,745; older, ≥50 years, n=79,517) and cigarette smoking histories (current smokers, recent quitters [quit <1 year ago], near-term quitters [quit 1-8 years ago], long-term quitters [quit >8 years ago], never smokers).

Results: Among younger adults, e-cigarette use increased in all groups of smokers, with notable increases between 2014 and 2018 among never smokers (1.3%-3.3%, adjusted prevalence difference=2%, p<0.001) and near-term quitters (9.1%-19.2%, adjusted prevalence difference=8.8%, p=0.024). Conversely, the only substantial increase in e-cigarette use between 2014 and 2018 among middle-aged (5.8%-14.4%, adjusted prevalence difference=8.2%, p<0.001) and older (6.3%-9.5%, adjusted prevalence difference=3.3%, p=0.045) adults was among near-term quitters. The largest absolute population increase in e-cigarette users between 2014 and 2018 was among younger-adult never smokers (0.49-1.35 million), followed by near-term quitters among middle-aged (0.36-0.95 million), younger (0.23-0.57 million), and older (0.35-0.50 million) adults.

Conclusions: The continuous increase among younger-adult never smokers suggests a rise in primary nicotine initiation with e-cigarettes. The concomitant increase among near-term quitters of all age groups suggests continuing e-cigarette use among smokers who may have switched from cigarettes previously.