Increasing tobacco exposure linked to rise in oral cancer virus infection

CANCER DIGEST – Oct. 7, 2014 – People with higher levels of the tobacco-related chemicals in their blood and urine were more likely to have the herpes virus that causes oral cancers, a new study shows.

While previous studies have shown higher risk of oral infection with the HPV16 virus among smokers, this study looked at HPV16 infection among people who have tobacco-linked chemicals in their blood or urine, regardless of how they are exposed to tobacco including second-hand smoke. The new study appears in the Oct. 7 issue of JAMA.

The study's 6,887 participants were drawn from the National Health and Nutrition Examination Survey, included 2,012 who were current tobacco users at the time of the study and 63 who were infected with HPV16.

Each increase in the blood level of the tobacco-related chemical cotinine, equivalent to three cigarettes per day, increased the odds of HPV16 prevalence by 31 percent. Each rising level of another tobacco chemical (NNAL) detected in urine, the equivalent of four daily cigarettes, increased the odds of HPV16 prevalence by 68 percent. This so-called dose-response curve is considered to be scientifically strong evidence of association between two events.

The biological reason for the association is unknown, but the researchers’ theory is that something about tobacco exposure may prevent the body from ridding itself of the virus.

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