This post honors Women’s History Month by focusing on a subject long-neglected by government-funded cancer investigators:
Why do American women who use smokeless tobacco have 10 times the risk for mouth cancer compared with American men who dip and chew tobacco?
This question arose in 2016, when Annah Wyss of the National Institute of Environment Health Science and 20 government-funded coauthors reported that American men had no excess mouth cancers associated with dipping or chewing tobacco (Odds Ratio, OR = 0.9), while American women, who mainly used powdered dry snuff, had ten times the risk (OR = 9) (here).
Those findings weren’t outliers. Epidemiologist Philip Cole and I in 2002 published a meta-analysis of smokeless tobacco and oral cancer (abstract here), concluding: “The use of moist snuff and chewing tobacco imposes minimal risks for cancers of the oral cavity and other upper respiratory sites, with relative risks ranging from 0.6 to 1.7. The use of dry snuff imposes higher risks, ranging from 4 to 13.”
Why did those 21 government-funded researchers, including one Debora Winn and at least seven other women, ignore these major differences?
Winn, as the first author of an epidemiologic study 43 years ago in the New England Journal of Medicine (abstract here), reported that “exceptionally high mortality from [oral cancer] among white women in the South is primarily related to chronic use of snuff. The relative risk associated with snuff dipping among white nonsmokers was 4.2.” That study led the public and the medical establishment to falsely believe that smokeless tobacco was responsible for an American oral cancer epidemic.
Winn had exaggerated her own findings. She claimed that smokeless tobacco
produced an “exceptionally high mortality from [oral cancer],” even though her
risk estimate only resulted in approximately 12 deaths per year among 100,000
long-term smokeless tobacco users. That mortality rate is not trivial, but it
is not “exceptionally high.” It is comparable to the annual death rate of 12 -15
per 100,000 users of automobiles – a figure that does not deter American
drivers.
Exaggeration is unacceptable, but Winn’s study has a special place in the
annals of American smokeless tobacco misinformation. It focused solely on a
niche tobacco product -- powdered dry snuff -- used by a tiny number of women
in the southern U.S. But this passage in Winn’s article assigned dry snuff’s
risk to all smokeless products: “The carcinogenic hazard of oral snuff is of
special concern in view of the recent upswing in consumption of smokeless
tobacco in the United States.” This misleading statement was featured in an AP
wire story that was published throughout the nation.
Winn’s results actually did not apply to chewing tobacco and moist snuff,
popular American smokeless products that have been used widely with
significantly fewer medical consequences than powdered dry snuff. Long after
her widely cited article was published, Winn acknowledged in two obscure
scientific forums that her results were specific to powdered dry snuff. In
1986, Winn was asked whether the patients in her study had used “dry snuff or
[moist] snuff.” She replied, “Almost exclusively dry snuff,” and then admitted
that “Dry snuff is now [in 1986] a minor portion of the U.S. market.” Her late
acknowledgment at a sparsely attended scientific meeting did nothing to deter
tobacco prohibitionists from misapplying her mortality claims to all smokeless
products, and to misdirection health professionals and the American public for
the next 40+ years.
