To assess with ¹H-MRS the potential effects of chronic cigarette smoking on cerebral metabolite concentrations.

43 tobacco dependent subjects were recruited from a smoking cessation program. PRESS-localized ¹H-MRS was performed in the second week after smoking cessation and additionally six months later (n=25) on a 1.5 T MR-System (Gyroscan ACS-NT, Philips Medical Systems). Two volumes of interest (VOI) were placed in the left prefrontal cortex and the anterior cingulate cortex. Absolute and relative concentrations of N-Acetylaspartate (NAA), total creatine (tCr) and choline containing compounds (Cho) were compared with ¹H-MRS data derived from 35 healthy controls.

Tobacco dependent subjects showed significantly decreased NAA concentrations in the anterior cingulate cortex compared to controls (p=0.01). This finding was independent from age but correlated highly with smoking history (p=0.001). Decreased NAA showed a tendency towards normalization after the six months follow-up. Further analysis revealed that subjects with higher tCr levels in the prefrontal cortex showed increased risk of relapse. Cho concentrations were significantly lower in females compared to males both in the anterior cingulated (p=0.004) and the left prefrontal voxel (p=0.02), independent from smoking history. NAA showed a tendency to decrease with age within the anterior cingulate cortex (p=0.05).

¹H-MRS results suggest that tobacco smoking leads to changes in specific brain regions (anterior cingulate cortex). Since the partition of axons is higher in anterior cingulate than in prefrontal cortex, the data concerning decreased NAA concentrations indicate that tobacco alters the viability of axons. tCr concentration in smokers was within the range of controls, but smokers with higher tCr level were more likely to relapse. ¹H-MRS of disorders associated with increased smoking prevalence (e.g. depression) have to account for the compounding effects of cigarette smoking.

Chronic cigarette smoking has adverse effects on neuronal viability in specific brain regions indicating that greater consideration of its potential impact regarding ¹H-MRS results is warranted.