Monday 18 September 2023

Looking back on the Enstrom-Kabat controversy

Geoffrey Kabat has reflected on the huge controversy over the secondhand smoke study he published with James Enstrom 20 years ago. It's well worth a read.

In the early 1990s, I had been a member of the EPA panel charged with evaluating the evidence for an association of passive smoking with lung cancer. It was clear that the leadership of the committee was intent on declaring that passive smoking caused lung cancer in non-smokers. I was the sole member of the 15-person panel to emphasize the limitations of the published studies—limitations that stemmed from the rudimentary questions used to characterize exposure. Many members of the committee voiced support for my comments, but in the end, the committee endorsed what was clearly a predetermined conclusion that exposure to secondhand smoke caused approximately 3,000 lung cancers per year among never-smokers in the United States.

... After several years of work, our paper was published by the BMJ on May 17th, 2003, addressing the same question Takeshi Hirayama had posed 22 years earlier in the same journal: whether living with a spouse who smokes increases the mortality risk of a spouse who never smoked. Based on our analysis of the American Cancer Society’s data on over 100,000 California residents, we concluded that non-smokers who lived with a smoker did not have elevated mortality and, therefore, the data did “not support a causal relation between environmental tobacco smoke and tobacco related mortality.”

The publication caused an immediate outpouring of vitriol and indignation, even before it was available online. Some critics targeted us with ad hominem attacks, as we disclosed that we received partial funding from the tobacco industry. Others claimed that there were serious flaws in our study. But few critics actually engaged with the detailed data contained in the paper’s 3,000 words and 10 tables. The focus was overwhelmingly on our conclusion—not on the data we analyzed and the methods we used. Neither of us had never experienced anything like the response to this paper. It appeared that simply raising doubts about passive smoking was beyond the bounds of acceptable inquiry.

As Kabat says, none of his critics was able to point to substantive flaws in the study. They just hated the conclusion and resorted to ad hominem attacks. Looking back, the remarkable thing isn't so much the backlash as the fact that the British Medical Journal published it at all. It is almost unthinkable that one of the big medical journals would publish anything that challenges the 'public health' lobby today.  

Incidentally, you can read the journal's referee comments from 2003 here.

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