Thursday, February 26, 2004

Very bad news 

'Oral Sex Shown to Be Linked to Mouth Cancer' -- headline, Associated Press.

Actually, the title of this post is tongue in cheek(!).

This study is a good example of epidemiology run amok. See Iain Murray's article at Tech Central Station. Murray asks whether modern epidemiology is "in danger of becoming a 'pathological science' because it had devolved into a data dredging exercise, mindlessly searching an ever-expanding pool of danger for marginally significant associations unpredicted by any a priori hypothesis."

In this case, the study's authors agree that heavy smoking and/or drinking cause between 75 - 90 percent of all oral cancers. Nevertheless, they found the presence of human papilloma virus in a retrospective study of "patients from Europe, Canada, Australia, Cuba and the Sudan with oral cancer and more than 1,700 healthy people." It turns out that the patients with oral cancer were three times as likely to admit to having participated in oral sex as those who did not have it.

Setting aside the well-understood problems with retrospective studies (they are by their nature so problematic that the FDA no longer accepts them as evidence of much of anything), the publicity around this oral sex study will undoubtedly miss the big picture: avoid oral cancer by avoiding tobacco, drinking in moderation, and going to a dentist that will inspect your mouth for precancerous lesions.


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