Chronic smoking affects nerve cells: study

Chronic smoking affects nerve cells and alters the chemical makeup of the brain, a new study has said.

This is the first imaging study to focus on the relationship between brain metabolites and nicotine dependence, Okan Gur, from the Department of Radiology at the University of Bonn in Germany said.

"The researchers used proton magnetic resonance spectroscopy to study 21 men and 22 women in the age group of 21 to 59 in a smoking cessation programme two weeks after they had quit and again six months later," Gur said at the 92nd meeting of the Radiological Society of North America, the world's largest annual medical meeting where 70,000 radiologists have assembled.

In the research, patients were encouraged to use nicotine patches during the initial six weeks of smoking cessation. However, only 36 of the patients continued.

Proton MRS measures brain metabolism at the cellular level and can provide detailed chemical data about brain's metabolites, which are involved in many physical and chemical process within the body.

The researchers compared the data collected from smokers to proton MRS data collected from 35 (age-and-gender matched) healthy controls.

The results showed that the nicotine-dependent patients had significantly decreased concentrations of the amino acid N-acetylaspartate in the anterior cingulated cortex, part of the brain that processes pleasure and pain.

The decreased NAA levels were evident regardless of whether or not the patient used a nicotine patch and correlated directly with the patient's smoking history: the greater the number of pack years (one pack per day for one year equals one pack year), the lower the NAA level.

The ACC is involved in mediating conditioned reinforcement, craving and relapsing behaviour in addiction, study co-author Christian G Schutz from the Department of Psychiatry at the University of Boon, said.

Reduced NAA levels have been reported for a number of psychiatric and mood disorders, including schizophrenia, dementia and bipolar disorder, as well as in cases of substance abuse, particularly alcohol dependence.

Upon follow-up after six months, the researchers found that most metabolite concentrations, including that of NAA, had normalised in the 25 ex-smokers who did not relapse.

These findings further emphasise the importance of quitting smoking. The degree of reduction of NAA in the ACC depends on the amount of tobacco consumed over time, but it appears to normalise after smoking cessation, Gur added.