“E-Cigarettes and Respiratory Disease: A Replication, Extension, and Future Directions”, 2020-07-01 (; backlinks; similar):
Electronic cigarettes show potential to reduce the harms from smoking combustible tobacco, but there is uncertainty about the long-term health consequences.
We replicate and extend the study by 2019, which reports longitudinal statistical associations between e-cigarette use and long-term respiratory disease.
We are able to closely replicate their results. When we use a more flexible empirical specification, among respondents who had never smoked combustible tobacco, we find no evidence that current or former e-cigarette use is associated with respiratory disease. The statistical associations between e-cigarette use and respiratory disease are driven by e-cigarette users who are also current or former smokers of combustible tobacco. A striking feature of the data is that almost all e-cigarette users were either current or former smokers of combustible tobacco. We then discuss the potential for future applied econometric research to credibly identify the causal effects of e-cigarette use on health. Challenges include the potential selection biases that stem from the complex set of consumer choices to initiate and quit smoking combustible tobacco, use of e-cigarettes, and dual use of both products. We suggest using a variety of identification strategies to uncover the causal effects that use a variety of econometric methods.
…In this paper we replicate and extend the analysis of a recent study by 2019, (hereafter B & G) of the association between e-cigarette use and long-term respiratory disease. B & G analyzed observational data from the first 3 waves of the Population Assessment of Tobacco and Health (PATH) Study. Based on statistically-significant longitudinal associations between former and current e-cigarette use and respiratory disease, B & G conclude that: “Use of e-cigarettes is an independent risk factor for respiratory disease in addition to combustible tobacco smoking.” Major news media reported the results, including NBC (2019), Reuters (2019), and National Public Radio (NPR 2019). For example, NPR reported that the study “found that people who used only e-cigarettes had about a 30% increased risk of developing lung disease, compared with people who didn’t use any nicotine products.” (NPR 2019, emphasis in the original). The accompanying press release (2019) and news media reports interpreted the estimated associations as showing that e-cigarettes are “harmful on their own” (Glantz, quoted in 2019).
…A striking feature of the PATH data analyzed by B & G is that almost all e-cigarette users were either current or former smokers of combustible tobacco. In the longitudinal analysis sample with 17,601 observations, there were only 12 current e-cigarette users who had never smoked combustible tobacco. None of the 12 respondents had incident (new) respiratory disease. The number of respondents who only used e-cigarettes is simply not large enough to draw meaningful conclusions about the independent association between e-cigarette use and respiratory disease. More recent data sets will face similar limitations, although to a lesser extent. For example, in the 2018 National Health Interview Survey data the prevalence of current e-cigarette use among people who had never smoked cigarettes was 1.1% ( et al 2020).