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The risk of developing an acoustic neuroma was greatly reduced among male smokers, but not among those who take snuff, researchers reported.

Current smokers had a 59% reduction in the risk of the benign tumor, compared with controls, while there was no risk decrease for snuff users, according to Sadie Palmisano, MS, of Ohio State University in Columbus, and colleagues.

Since both smokers and snuff users had similar levels of nicotine in their blood, the finding appears to rule out a protective role for the chemical, Palmisano and colleagues reported online in the American Journal of Epidemiology.

"We see this effect with current smokers but don't see it with current snuff users," Palmisano said in a statement, "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."

An acoustic neuroma is a benign, slow-growing tumor of the Schwann cells of the eighth cranial nerve, the researchers noted. Also known as vestibular schwannoma, the disease makes up between 8% and 10% of all intracranial tumors.

Two previous studies had found an apparent protective role for smoking. In 2007, researchers found that current smokers, both male and female, had a 50% reduction in risk of acoustic neuroma, while the 2010 report of the British Million Women Study found that female smokers had a 59% risk reduction.

Both studies suggested that nicotine might be the protective agent, the researchers noted, so, to investigate the issue, they conducted a case-control study among smokers and users of smokeless tobacco in Sweden.

For the period Sept. 1, 2002 through Aug. 31, 2007, the researchers enrolled 451 people newly diagnosed with acoustic neuroma. They were matched for age, sex, and place of residence with 710 healthy controls.

Analysis showed a significant protective effect for male smokers. The odds ratio was 0.41, with a 95% confidence interval from 0.23 to 0.74.

Women smokers also appeared to be protected, but to a lesser and nonsignificant degree. The odds ratio was 0.70, with a 95% confidence interval from 0.40 to 1.23.

The researchers only evaluated the effect of snuff use among men, because there were too few women who used the substance to make meaningful inferences.

But among men, using snuff had no effect. The odds ratio for acoustic neuroma, given smokeless tobacco use, was 0.94, with a 95% confidence interval from 0.57 to 1.55.

Although the study rules out a role for nicotine, Palmisano and colleagues suggested that a lack of oxygen associated with smoking might starve the Schwann cells, preventing the tumor overgrowth.

They cautioned, however, that Swedish and American snuffs have different characteristics, so the findings may not apply directly to American smokeless tobacco users.

They added that the study should not be taken as an endorsement of smoking to prevent acoustic neuroma, but as providing "rare clues" to the causes of a rare tumor about which little is known.