Tobacco Use Tied to Viral Infections That Trigger Oral Cancers

A latest study reveals a significant link between use of tobacco and infection with oral papillomavirus type 16 (HPV16).

HPV16 is a sexually transmitted virus that is responsible for mouth and throat cancer worldwide. Over the past two decades, the rate of such cancer has increased by 225 percent in the United States. It is estimated that nearly 80 percent of the cancers are located in the back of the throat and is transmitted through oral sex.

In this study, researchers at Johns Hopkins found existence of a strong link between tobacco use or exposure and infection with oral human papillomavirus type 16. This infection is more common among those who have recently been exposed to or used tobacco, independent of their sexual behavior.

"The practice of oral sex is common, but this cancer is rare. So there must be cofactors in the process that explain why some people develop persistent HPV16 infections and HPV-positive oropharyngeal cancers when most other people don't," said Gypsyamber D'Souza, Ph.D., M.S., M.P.H., an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health and Johns Hopkins Kimmel Cancer Center.

However, it is still a mystery as to why tobacco ups the likelihood of oral HPV16 infection. But, the researchers suspect that the virus may not be completely eliminated from the body as easily in those who use tobacco. They also caution that although the study reveals an independent link between tobacco and the infection, they do not rule out the possibility that those who use more tobacco might also indulge in more oral sex due to which they have greater risk of the infection.

This latest finding supports the previous studies that have revealed the relation between cigarette use and oral HPV16 infection. The researchers state that smoking or using other forms of tobacco do not directly trigger the infection and even non-smokers can get infected with HPV16.

They based their finding on the evaluation of 6,887 participants who were a part of the National Health and Nutrition Examination Survey. They also included 2,012 who were current tobacco users at the time of the study and 63 who were infected with the virus.

Using a 30-second oral rinse and gargle that collected the throat and mouth cells, the researchers detected the virus. Apart from this, tobacco use was reported and samples of blood and urine was submitted. These samples were used to test two tobacco-related chemicals, mainly cotinine and NNAL (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol).

Rise in cotinine level in the blood, equal to three cigarettes each day, elevated the risk of HPV 16 by 31 percent.

"These results may provide an additional reason for smoking cessation and suggest that even modest amounts of tobacco use are associated with higher oral HPV prevalence," said Fakhry.

The finding was documented in the issue of JAMA.