To the Editor:

Harlow and colleagues’1 study accounting for time-dependent confounders in the U.S. PATH study supports the hypothesis that e-cigarette use is responsible for a considerable share of cigarette initiation among US youth. This questions the definition of epidemiology, which is not only “the method used to find the causes of health outcomes and diseases in populations” but also “the application of this study to the control of health problems.”2 I’m afraid that the latter is an incantation flying in the face of an enduring lack of public health interventions to control and prevent disease. Indeed, evidence has long been accumulating that the e-cigarette is a gateway to smoking,3 as expected from good, common sense.4 How can the US Food and Drug Administration continue to authorize the sale of e-cigarettes? On April 26, it issued decisions on multiple NJOY Ace e-cigarette products. As previously with Logic, it did not publish the full Technical Project Lead document detailing the scientific justification for its decision but only one tenth of the document, most of it only about legal requirements. Finally, risk minimization measures are not yet a concern.

REFERENCES 1. Harlow AF, Stokes AC, Brooks DR, et al. E-Cigarette use and combustible cigarette smoking initiation among youth: accounting for time-varying exposure and time-dependent confounding. Epidemiology. 2022;30:523–532. 2. Centers for Disease Control and Prevention. Principles of epidemiology in public health practice: an introduction to applied epidemiology and biostatistics. U.S. Department of Health and Human Services, 2006. Atlanta. 3. Watkins SL, Glantz SA, Chaffee BW. Association of noncigarette tobacco product use with future cigarette smoking among youth in the population assessment of tobacco and Health (PATH) Study, 2013-2015. JAMA Pediatr. 2018;172:181–187. 4. Braillon A. Electronic cigarettes: from history to evidence-based medicine. Am J Prev Med. 2014;47:e13.