Smokeless Tobacco May Affect Motor Skills

WebMD Feature

Feb. 21, 2000 (Salem, N.Y.) -- In a pilot study supported by the Smokeless Tobacco Research Council and described in the September 1999 issue of Nicotine & Tobacco Research, researchers describe what happened when 10 smokeless tobacco users and 11 nonusers tried to adapt to new conditions in a test of visual-motor skills. The study participants looked at a computer monitor that displayed real-time tracings of the movements of an electronic-pen tip. Without being able to see their arm movements, the subjects moved the pen along a digitizing tablet to hit targets on the screen. During the test, the researchers altered the participants' visual feedback by rotating the image 45 degrees so that they had to learn by trial and error to relate the movement of their hand or arm to what they saw on the screen.

Chewing tobacco produced "larger normalized jerk scores" or less smooth movement after the image was rotated and immediately after it was returned to normal.

"I don't think you would see a difference in the performance of normal everyday tasks where you don't need to learn something new," says Jose Contreras-Vidal, Ph.D., an assistant professor at the University of Maryland, College Park, and lead author of this study. But the results do indicate that tobacco use may affect a person's learning capability related to complex tasks, such as learning to drive a new car, which involves adjusting to variables such as how it steers, brakes, and accelerates.

The researchers suspect that nicotine is responsible for these possible effects, because it affects the release of the neurotransmitter dopamine in the brain. As Contreras-Vidal notes, dopamine plays a critical role in the control of movement.

The study "is a novel approach to looking at the effects of nicotine on fine motor control," says Stephen Heishman, PhD, senior researcher at the National Institute on Drug Abuse, National Institutes of Health, Baltimore, Md. "I tend to view the results with a bit of caution and think of them as preliminary findings until they can be replicated."

Contreras-Vidal agrees. "We need now to do a large-scale study, to better control the levels of nicotine," he says, "but these results are remarkable and they should be taken seriously."

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