Bilateral Fronto-Parietal Integrity in Young Chronic Cigarette Smokers: A Diffusion Tensor Imaging Study

Cigarette smoking continues to be the leading cause of preventable morbidity and mortality in China and other countries. Previous studies have demonstrated gray matter loss in chronic smokers. However, only a few studies assessed the changes of white matter integrity in this group. Based on those previous reports of alterations in white matter integrity in smokers, the aim of this study was to examine the alteration of white matter integrity in a large, well-matched sample of chronic smokers and non-smokers.Using in vivo diffusion tensor imaging (DTI) to measure the differences of whole-brain white matter integrity between 44 chronic smoking subjects (mean age, 28.0±5.6 years) and 44 healthy age- and sex-matched comparison non-smoking volunteers (mean age, 26.3±5.8 years). DTI was performed on a 3-Tesla Siemens scanner (Allegra; Siemens Medical System). The data revealed that smokers had higher fractional anisotropy (FA) than healthy non-smokers in almost symmetrically bilateral fronto-parietal tracts consisting of a major white matter pathway, the superior longitudinal fasciculus (SLF).We found the almost symmetrically bilateral fronto-parietal whiter matter changes in a relatively large sample of chronic smokers. These findings support the hypothesis that chronic cigarette smoking involves alterations of bilateral fronto-parietal connectivity

Nicotine Effects on White Matter Microstructure in Male and Female Young Adults

Nicotine use is still widely prevalent among adolescents and young adults. Nicotine use is associated with white matter microstructural changes as measured by diffusion tensor imaging (DTI), a magnetic resonance imaging technique that measures the diffusion of water in the brain. In adults, nicotine use is generally associated with poorer white matter microstructure, exhibiting lower fractional anisotropy (FA), but in adolescents/young adults, microstructure appears healthier, as indicated by higher FA. No study has examined gender differences in the effects of nicotine on white matter microstructure in young adults. 53 subjects (18 nicotine users [10 female] and 35 controls [17 female]) underwent an MRI scan, neuropsychological battery, toxicology screening, and drug use interview. Nicotine group and gender*nicotine group were used to predict FA and mean diffusivity (MD) in various white matter tracts. In significant tracts, axial (AD) and radial (RD) diffusivity were measured. Nicotine users exhibited significantly lower FA than controls in the left anterior thalamic radiation, left inferior longitudinal fasciculus, left superior longitudinal fasciculus—temporal, and left uncinate fasciculus. In these tracts, AD and RD did not differ, nor did MD differ in any tract. The gender*nicotine group interaction did not predict any diffusion measures. These results are inconsistent with other adolescent/young adult studies, likely due to methodological differences and a slightly older sample. Further studies should examine the longitudinal effects of nicotine use and gender in a larger sample

Clusters of increased fractional anisotropy (FA) in smokers compared to healthy non-smokers.

<p>Significant FA alterations as revealed by voxel-based whole brain analysis with SPM5 displayed on the FA average map of the sample. Voxels of increased FA in smokers revealed by SPM5 analysis are displayed with red colour. All clusters shown exceed an uncorrected statistical threshold of P<0.001 and a cluster size threshold of 100 consecutive voxels.</p

Demographic characteristics of the smokers and never-smokers studied.

a<p>significantly different from control group, p<0.01.</p>b<p>three participants reported drinking more than once a week among smokers and no non-smoking participants reported drinking more than once a week.</p>c<p>Before MRI acquisition run, participants were asked to rank their craving from 0 (“not at all”) to 10 (“extreme”).</p

Group Comparison of Increased Fractional Anisotropy (FA) in White Matter.

<p>Uncorrected p<0.001, 100 voxel minimum extent.</p