Melissa Harrell and her colleagues just published important quantitative information adding to the case that e-cigs are promoting rather than replacing cigarette smoking among youth. Their new paper, “Impact of the e-cigarette era on cigarette smoking among youth in the United States: A population-level study,” estimates changes in youth smoking prevalence after 2014 when e-cig use became widespread among US youth. They find that the rate of decline of smoking prevalence was cut about in half after 2014, from 0.75%/year before 2014 to 0.38%/year after 2014. Even allowing for a sudden drop of -1.64% in 2014, the difference between the pre-2014 trend and what actually happened amounted to 1.7 million extra middle and high school smokers from 2014 to 2019 (graph above).
As Harrell and her colleagues point out, their analysis supports the conclusion that e-cigs are a gateway to smoking. If they were diverting youth from cigarettes, the decline in smoking would have accelerated not decelerated. They also have a nice discussion of other related studies that have drawn different conclusions, mostly because they were based on fewer years of data so did not have enough information to reliably detect the changes that occurred after ecig use among youth became widespread.
While not a limitation of the paper, it is important to keep in mind that their analysis only assesses one of the two gateway “doors,” the interaction between e-cigarette and cigarette use. E-cigs have also dramatically expanded the nicotine addiction market by attracting low risk youth would would be unlikely to initiate nicotine use with conventional cigarettes. This is another important fact that e-cig advocates ignore.
This paper also implicitly raises and important policy question for the FDA: How many smokers lives have been saved by the e-cigarettes it allows to remain on the market? FDA still has not told the public how many adult smokers it trades off for every new kid e-cigs addict. They need to tell us.
Here is the abstract:
To examine and compare trends in past 30-day cigarette smoking among adolescents in the US from 2002 to 2019, before and after the onset of the “e-cigarette era” in 2014. Using National Youth Tobacco Survey (NYTS) data from 2002 to 2019, we modeled the prevalence of past 30-day cigarette smoking over time. A total of n = 274,551 (weighted N = 340,403,754) middle and high school students were included in this study. Interrupted time series analyses were used to examine changes in cigarette smoking over time and compare trends in cigarette smoking pre- and post-2014. Models were applied to the full sample and stratified by middle (6th-8th grade) and high school (9th-12th grade). The observed number of current adolescent cigarette smokers post-2014 was compared to the predicted number, given trends in cigarette smoking prevalence observed pre-2014. Among all students, past 30-day cigarette smoking declined by approximately 0.75% per year from 2002 to 2013 (p < 0.001). Following a significant drop in prevalence from 2013 to 2014 (1.64%; p < 0.001), the decline in past 30-day cigarette smoking slowed significantly to approximately 0.37% per year (p < 0.001), from 2015 to 2019. We estimate that the onset of the “e-cigarette era” in 2014 corresponded to over 1.66 million (95% CI: 1.57 m – 1.75 m) more past 30-day cigarette smokers from 2015 to 2019, cumulatively. The rate of decline in past 30-day cigarette smoking prevalence among adolescents observed since 2002 slowed with the onset of the “e-cigarette era” in 2014, providing evidence at a population-level for the “gateway effect.”
The full citation is: Harrell MB, Mantey DS, Chen B, Kelder SH, Barrington-Trimis J. Impact of the e-cigarette era on cigarette smoking among youth in the United States: A population-level study. Prev Med. 2022 Sep 22;164:107265. doi: 10.1016/j.ypmed.2022.107265. Epub ahead of print. PMID: 36152819. It is available here.