Another UC San Francisco E-Cigarette Gateway Claim, Based on Tiny Numbers

Last week I called for retraction of a flawed study by University of California San Francisco’s Benjamin W. Chaffee, Shannon Lea Watkins and Stanton A. Glantz that appeared in the journal Pediatrics (here and here).  

Once again using the FDA Population Assessment of Tobacco and Health (PATH) survey, the same authors exaggerated the gateway effect of e-cigarettes, hookah and smokeless tobacco in a January JAMA Pediatrics article (here).  I criticized at that time the omission of information that would have provided context for their findings (here).  The exaggerations were amplified in the media.

In an interview with National Public Radio (here), Dr. Watkins failed to note the minuscule numbers used in her study to support the gateway claim.  I have inserted those numbers in bold in her quote, here:

“We found that kids who tried e-cigarettes [n=11] or hookah [n=8] or smokeless tobacco [n=3] or cigars [n=7] – any noncigarette tobacco product – were all twice as likely to try cigarettes a year later compared to kids who hadn’t used any of those other tobacco products [n=175].  Kids who were using two or more noncigarette products [n=15] were four times as likely to report using cigarettes a year later.” (I have confirmed these numbers in the FDA data; they are in the table below)

Dr. Watkins added the extraordinary claim that trying one tobacco product changes one’s perception of cigarettes: “Using these products might change a kid’s perception of the harm of cigarettes, and so they are perceived as less dangerous and they get used to using tobacco and so using conventional cigarettes is not so scary or ‘bad’.”

In her view, trying a tobacco product causes one to change friends: “It will expose them to different kinds of kids, maybe kids that are already using conventional cigarettes, and then they might go on to try them.”

Instead of sharing her conjecture on how e-cigarettes led 11 children to begin smoking, Dr. Watkins should have focused on the fact that 80% of the 219 new smokers [n=175] in her study had not previously used any tobacco product.

Odds Ratios And Numbers of Teens Smoking Cigarettes After One Year, According to Ever Tobacco Status at Baseline
Ever Tobacco Status- Baseline (n)	Odds Ratio	Number Smoking At One Year (%)
Never tobacco use (9,058)	Referent	175 (79.9)
E-cigarettes (255)	2.12	11 (5.0)
Hookah (189)	2.15	8 (3.7)
Other combustible (114)	3.08	7 (3.2)
Smokeless tobacco (93)	1.53	3 (1.4)
Two or more products (200)	3.81	15 (6.8)
All (9,909)		219 (100)

Tobacco Gateway Report Omits Important Information

Here we go again.  Another federally funded study from the University of California, San Francisco, claims that “Nonsmoking adolescents who use e-cigarettes, smokeless tobacco or tobacco water pipes are more likely to start smoking conventional cigarettes within a year.” (UCSF press release here)  Researchers analyzed data on some 10,400 teens enrolled in the Population Assessment of Tobacco and Health (PATH) Survey in 2013-2014, then followed up with the subjects one year later.

“We found that teens who experimented with tobacco in any form were at greater risk of future smoking,” said senior author Dr. Benjamin W. Chaffee; his study appears in JAMA Pediatrics.

The researchers report that teens who had ever used e-cigarettes, hookah, other combustible products or smokeless tobacco at the baseline survey were two or three times as likely to be smoking cigarettes (in the past-30 days) one year later than those who had not tried any tobacco product.  Those who had tried two or more products were 3.8 times more likely to be smoking.

The authors used a sophisticated analysis to arrive at these results, but news stories describing this as evidence of a gateway to teen smoking (examples here and here) are inaccurate.

Chaffee and his colleagues, including anti-tobacco crusader Stanton Glantz, omitted information that is critical to putting their findings in perspective.  Although teens trying other tobacco products were more likely to smoke, the majority of new smokers after one year came from the group that had not tried tobacco at baseline.  I offer the following calculations based on obscure information in the published article.

Odds Ratios (ORs) And Numbers of Teens Smoking Cigarettes After One Year, According to Ever Tobacco Status at Baseline
Ever Tobacco Status- Baseline (n)	Odds Ratios	Number Smoking At One Year (%)
Never tobacco use (9,058)	Referent	175 (79.9)
E-cigarettes (255)	2.12	11 (5.0)
Hookah (189)	2.15	8 (3.7)
Other combustible (114)	3.08	7 (3.2)
Smokeless tobacco (93)	1.53	3 (1.4)
Two or more products (200)	3.81	15 (6.8)
All (9,909)		219 (100)

After one year, 219 teens had smoked a cigarette in the past 30 days, and 175 of those (80%) had never used any tobacco product at baseline.  Even though the odds of smoking were higher among youth who had tried other products, the number of smokers contributed by each of these groups was minuscule.  (While actual survey numbers may vary slightly, the relative contributions of the groups will not change.)

The Chaffee article emphasizes odds ratios but omits or obscures important contextual information.  While teens who try one tobacco product are more likely to try another, the dominant gateway in the PATH survey was from no previous tobacco use to cigarettes.

No underage tobacco initiation is acceptable; neither is misdirection by researchers.

The Bitter Truth: CDC’s Numbers on Flavored Tobacco Don’t Add Up

Tobacco opponents routinely focus their ire on flavorings.  The CDC recently launched the latest attack, based on its analysis of the 2014 National Youth Tobacco Survey.  The agency reported that “Among middle and high school students in 2014, an estimated 1.58 million used a flavored e-cigarette, 1.02 million used flavored hookah tobacco, 910,000 used flavored cigars…in the past 30 days”

The survey asked students about past 30-day use of each product; in a separate section, students were queried on their use of flavored e-cigarettes, hookah and cigars.  Here are the numbers:

Number of Middle and High School Students Who Used Selected Tobacco Products and Flavored Products in the Past 30 Days
		Number of Students
E-Cigarettes	Flavored E-Cigarettes
Yes	No	920,000
Yes	Yes	1,580,000
NO	YES	360,000
Hookah	Flavored Hookah
Yes	No	660,000
Yes	Yes	1,020,000
NO	YES	310,000
Cigars	Flavored Cigars
Yes	No	530,000
Yes	Yes	910,000
NO	YES	240,000

The data is full of contradictions: 360,000 students reported that they had used flavored e-cigarettes in the past 30 days, but they hadn’t used e-cigarettes in the past 30 days.  Twenty three percent (310,000) who reported using flavored hookah in the past 30 days also said they had not used hookah in the past 30 days. Twenty-one percent (240,000) who reported using flavored cigars in the past 30 days also said they had not used cigars in the same period.

How did the CDC deal with these discrepencies?  The agency briefly mentioned them as a limitation and said those students were not counted.

The inconsistencies cannot be so easily ignored, particularly as contradictory responses were not restricted to the flavor questions.  For example, of the 1.68 million students who reported smoking cigarettes in the past 30 days, almost 12% responded in other questions that they had never smoked or had not smoked in the past 30 days.    

Kids may say the darndest things, but their survey results should not be spun by the CDC into national tobacco control policy.  Rather, the agency should issue a comprehensive report on the internal consistency and relative validity of the NYTS data.