Tuesday, 12 May 2020

The PATH that leads to understanding the vaping epidemic

Finding the PATH

Since 2013, there has been a remarkable survey operating in the United States that has deepened our understanding of tobacco and e-cigarettes use and consequences. It is the Population Assessment of Tobacco and Health Survey (PATH) - a longitudinal, nationally representative survey of 46000 Americans. This survey generates information on tobacco and e-cigarette use behaviours, and with its longitudinal design it interviews the same individuals every year. It is planned that the survey will continue at least until 2024.

Exploring the PATH

Data from this survey has already been analyzed and there at least 104 publications using PATH data. From these studies we have learned, for example, that e-cigarette users are more likely to progress to becoming combustible cigarette users, and that, in a longitudinal analysis, e-cigarettes use was associated with lung disease.

Following the PATH to more new discoveries

Recently, a multidisciplinary, multi-agency team of scientists has taken a deep dive into the PATH longitudinal data to explore the process of becoming a tobacco or e-cigarette user. Their findings were published this month in 10 papers in a special supplement to the journal Tobacco Control.

From cross-sectional data we can count the numbers of smokers, former smokers and never smokers, but we cannot discover how one moves from one behaviour to another. That can be learned from longitudinal data and that was the focus of this recently published work. Researchers studied the movements from one state to another as shown here: 




This diagram is actually a simplified depiction of the number of changes of state that can occur, as as it does not show movement from one product category to another. British American Tobacco also pays attention to how people move into and out of tobacco use and how they move from one product to another. Their diagrammatic representation of this process is considerably more complicated.



The simplified model of transitions shown in the Figure "Behavioral Transitions" can be applied to each product -- e-cigarettes, combustible cigarettes, cigars, hookah and smokeless tobacco. Further complication can be added by studying multiple use of products and movement from one product to another.

The papers in the Tobacco Control supplement address all these subjects, although the results are not presented in the most accessible style. However, the most widely used products are e-cigarettes and combustible cigarettes, so we will examine the findings concerning these products more closely.

Cigarette Smoking

Most of those who had smoked a cigarette in the past month in 2013-14 had done so again two years later. Fewer than one-third (29%) of youth, one-quarter (25%) of young adults and one-seventh (15%) of adults had two quit smoking two years later. Among those who had stopped in the year between, one-tenth of youth (11%) and one-thirtieth of adults (3%) had returned to smoking the following year.




E-cigarettes (ENDS)

It should be kept in mind that these papers study the first three waves of the PATH study, ending in 2016. The rise of closed-pod systems such as JUUL and other copycat brands that have grown to epidemic proportions among our youth has occurred since that date.

Still, trends up to 2016 show that there was already a developing youth epidemic of e-cigarette use. From Wave 1 to Wave 3 (2013 to 2016), use by youth (12-17) of e-cigarettes in the past 30 days grew from 3% to 4%. Among young adults (18-24), past 30-day use grew from 13% to 17%. Some of this e-cigarette use was experimental.

By Wave 3 (2016), 54% of the youth that had been using e-cigarettes at Wave 1 had discontinued e-cigarette use. The corresponding figure for young adults was 62%.




Poly-tobacco use 

The diagrams from the papers shown above do not capture the degree to which young people and adults use both cigarettes and e-cigarettes, although this PATH study confirms that most of those who used e-cigarettes were also smoking.

Among young adults, almost half of those who only used e-cigarettes at Wave 1 had stopped using any tobacco product over the two study waves (46%). Among those who used both e-cigarettes and combustible cigarettes, the proportion who ceased use of all nicotine products was much lower -- slightly more than 1 in 10 (12%). (Table 1)

Stanton et al, the authors of another study of PATTY data similarly concluded:
"The majority of ENDS use is polytobacco use, and ENDS polytobacco users who also use cigarettes are less likely to stop using tobacco 2 or 3 years later compared with exclusive ENDS users."

PATH-type studies in Canada?

There is currently no direct equivalent to the PATH study in Canada.

Previous longitudinal surveys involving smokers included the Survey on Smoking in Canada, which was launched in 1994 to assess the impact after the federal government cut tobacco taxes; the National Population Health Survey, which was in the field for more than a decade and the Ontario Tobacco Survey  which collected data from 2005 to 2011.

The COMPASS survey, managed through the University of Waterloo, is an ongoing longitudinal survey of school children across Canada.