Retract the UC San Francisco E-Cigarette “Gateway” Study

Some published articles are so flawed that they deserve retraction.   

A case in point is the Pediatrics article by University of California San Francisco's Benjamin W. Chaffee, Shannon Lea Watkins, and Stanton A. Glantz (here) that features a totally baseless claim: “Among adolescent cigarette experimenters, using e-cigarettes was positively and independently associated with progression to current established smoking.” 

Using Wave 1 of the FDA Population Assessment of Tobacco and Health (PATH) survey, Chaffee et al. define teen experimental smokers as having smoked “in your entire life” anywhere from “1 or more puffs but never a whole cigarette” up to 99 cigarettes.  They divide experimental smokers into three groups according to e-cigarette use: never users, past 30-day users and ever triers.  In their analysis, controlling for numerous variables, e-cigarette users at Wave 1 had higher odds of having consumed 100+ cigarettes or having smoked in the past 30 days at follow-up one year later.

The findings and the claim are false. In their analysis, the authors ignore the fact that their study group consisted entirely of experimental smokers with widely varied experience – one or more puffs but never a whole cigarette, one cigarette, 2-10, 11-20, 21-50 and 51-99 cigarettes. 

Using the PATH data, my research team reproduced Chaffee’s analysis and Pediatrics published our results online (here).  The table we submitted to the journal was published in an unreadable fashion, so we offer it here.

Odds Ratios (95% Confidence Interval) for Smoking Outcomes in the Wave 2 PATH Survey, According to E-Cigarette Use at Wave 1
Wave 2 Outcome (1 year)	Chaffee’s Results	BR-NP	BR-NP + Wave 1 LCC
Smoked 100+ Cigarettes
Never E-Cig	Referent	Referent	Referent
E-Cig Past 30 Days	2.56 (1.58 – 4.14)	2.60 (1.61 – 4.19)	1.21 (0.69 – 2.13)
E-Cig Trier	2.13 (1.43 – 3.18)	2.16 (1.46 – 3.22)	1.45 (0.88 – 2.38)
Smoked Past 30 Days
Never E-Cig	Referent	Referent	Referent
E-Cig Past 30 Days	2.29 (1.64 – 3.19)	2.12 (1.52 – 2.96)	1.41 (0.998 – 2.00)
E-Cig Trier	1.56 (1.15 – 2.12)	1.43 (1.05 – 1.95)	1.09 (0.78 – 1.52)
Smoked 100+ Cigarettes and Smoked Past 30 Days
Never E-Cig	Referent	Referent	Referent
E-Cig Past 30 Days	2.56 (1.52 – 4.32)	2.55 (1.51 – 4.31)	1.32 (0.75 – 2.30)
E-Cig Trier	2.41 (1.46 – 3.97)	2.45 (1.49 – 4.03)	1.70 (0.96 – 3.01)

BR-NP, Rodu-Plurphanswat reproduction of Chaffee et al. odds ratios
 

When we added lifetime cigarette consumption (LCC), the positive results for e-cigarettes essentially disappeared, negating Chaffee’s core claim.

 

It is well established that past smoking (in this case, LCC at Wave 1) predicts future smoking (one year later).  Chaffee, Watkins and Glantz ignored this information in order to claim that e-cigarettes are a gateway to smoking.  Their study should be retracted.  

I will review in my next post Chafee’s published response to our comment.