Wednesday, December 4, 2013

The CDC Abuses the Facts About E-Cigarettes – Part I

The headline on the Centers for Disease Control’s September 5 press release was dire: “E-cigarette use more than doubles among U.S. middle and high school students from 2011-2012” (here).  The agency’s shocker generated reams of coverage (examples include USA Today, the Los Angeles Times, the Chicago Tribune and CBS News).

In an earlier blog post, I criticized the CDC’s media ploy for positioning e-cigarettes as a new childhood tobacco epidemic (here).  Based on additional research, I have uncovered serious flaws in the agency’s analysis – errors and omissions that made the CDC’s message more appealing to the media, but less conscionable in terms of public health.

Analyzing the 2012 National Youth Tobacco Survey (NYTS), the dataset the CDC used to generate its report, I discovered the falsehood of this key statement in the agency’s press release:  “Altogether, in 2012 more than 1.78 million middle and high school students nationwide had tried e-cigarettes.”  This assertion was highlighted in most major media reports.

In fact, the NYTS did not collect information on the number of students who had used e-cigarettes in 2012.  Instead, the survey asked if students HAD EVER TRIED e-cigarettes, “even just one time”; that number is 1.78 million.  The only number in the survey that is applicable to 2012 is the 554,179 students who used an e-cigarette on “at least one day” in the past month.  That is only 31% of the number wrongly reported by the CDC.

Another statement in the CDC release is seriously misleading: “The study also found that 76.3 percent of middle and high school students who used e-cigarettes within the past 30 days also smoked conventional cigarettes in the same period.”  That statement implies that 24% of e-cigarette users were not smokers, and gives the distinct impression that e-cigarettes are emerging as a first-use tobacco product.

Not so fast.  The NYTS also measured other forms of tobacco use, including smokeless tobacco, cigars, pipes, hookah, snus and dissolvable tobacco.  In addition to the 76.3% of e-cig users who were concurrent cigarette smokers, another 12.9% were using other tobacco products.  That means the percentage of e-cigarette users who weren’t using any other tobacco product was only 10.8%, a tiny fraction.  Of this group, about half had “ever tried cigarette smoking, even one or two puffs”. 

There is another feature of this and other federal surveys that you need to understand: the numbers that the CDC reports (e.g. 1.78 million) are not actual counts but are national estimates based on a complex sampling strategy.  This is not necessarily a problem, but it provides needed context, especially when the number of survey respondents is small.  For example, the total number of youths in this survey who used an e-cigarette in the past 30 days was 500, and the number of vapers who did not use any tobacco product nor had ever tried smoking was around 20.

The bottom line: Among all middle and high school e-cigarette users, only 10.8% were not concurrently using any other tobacco product, and half of those had tried to smoke in the past. 

CDC director Tom Frieden may wish to use his position as a bully pulpit to oppose e-cigarette use, but abusing the facts is inexcusable.

In a future post I’ll discuss other key findings from the NYTS that were omitted by the CDC.

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