Study suggests smoking, but not nicotine, reduces risk for rare tumor

New research confirms an association between smoking and a reduced risk for a rare benign tumor near the brain, but the addition of smokeless tobacco to the analysis suggests nicotine is not the protective substance.

The study using Swedish data suggests that men who currently smoke are almost 60 percent less likely than people who have never smoked to develop this tumor, called an acoustic neuroma. But men in the study who used snuff, which produces roughly the same amount of nicotine in the blood as smoking, had no reduced risk of tumor development.

“We see this effect with current smokers but don’t see it with current snuff users, so we think that maybe the protective effect has something to do with the combustion process or one of the other chemicals in cigarettes that are not in snuff,” said Sadie Palmisano, a doctoral student in epidemiology at Ohio State University and lead author of the study. “We learned something from exclusion.”

Acoustic neuroma is a tumor that grows on the vestibular cochlear nerve connecting the ear to the brain. It is not cancer, but it can cause nerve damage as well as symptoms that include vertigo, ringing in the ears and hearing loss. The only treatment for these slow-growing tumors is surgical removal or high-powered radiation that reduces their size. About one in 100,000 people per year develops these growths, which account for approximately 8 percent of all primary tumors inside the skull in the United States.

A few previous studies have found a similar link between smoking and lowered risk for development of these tumors, but did not take snuff use into account. Though the research is aimed at prevention of acoustic neuromas, the researchers emphasized that they do not endorse smoking as a way to avoid developing a tumor.

The findings suggested to the scientists that a lack of oxygen associated with smoking might help prevent the tumors by starving the cells whose overgrowth leads to the formation of an acoustic neuroma. These are called Schwann cells, and they produce the myelin coating on nerve cells in the peripheral nervous system outside the brain and spinal cord.

The research is published online and scheduled for future print publication in the American Journal of Epidemiology.

The scientists conducted a nationwide study of acoustic neuroma between 2002 and 2007, compiling data on Swedish patients between the ages of 20 and 69 years at the time of diagnosis with the tumors. These patients, as well as healthy Swedish control participants, also completed questionnaires about environmental exposures and lifestyle choices.

Palmisano and colleagues applied statistical analysis to these data to determine associations between smoking and snuff use and risk for acoustic neuroma. The analysis included data on 423 patients with tumors and 645 controls matched for age, sex and home location.