Abstract
The main purpose of this study is to examine the lifetime tobacco consumption and the degree of nicotine dependence related gray matter (GM) and white matter (WM) volume alterations in young adult-male smokers. Fifty-three long-term male smokers and 53 well-matched male healthy non-smokers participated in the study, and the smokers were respectively categorized into light and heavy tobacco consumption subgroups by pack-years and into moderate and severe nicotine dependence subgroups using the Fagerström Test for Nicotine Dependence (FTND). Voxel-based morphometry analysis was then performed, and ANCOVA analysis combined with subsequent post hoc test were used to explore the between-group brain volume abnormalities related to the smoking amount and nicotine dependence. Light and heavy smokers displayed smaller GM and WM volumes than non-smokers, while heavy smokers were found with more significant brain atrophy than light smokers in GM areas of precuneus, inferior and middle frontal gyrus, superior temporal gyrus, cerebellum anterior lobe and insula, and in WM areas of cerebellum anterior lobe. However, the contrary trend was observed regarding alterations associated with severity of nicotine dependence. Severe nicotine dependence smokers rather demonstrated less atrophy levels compared to moderate nicotine dependence smokers, especially in GM areas of precuneus, superior and middle temporal gyrus, middle occipital gyrus, posterior cingulate and insula, and in WM areas of precuneus, posterior cingulate, cerebellum anterior lobe and midbrain. The results reveal that the nicotine dependence displays a dissimilar effect on the brain volume in comparison to the cigarette consumption. Our study could provide new evidences to understand the adverse effects of smoking on the brain structure, which is helpful for further treatment of smokers.
Highlights
Smoking, which is one of the most critical and preventable causes of morbidity and mortality, has always been a thriving focus in research studies
We administered the same questionnaire designed for the use in the 2010 Global Adult Tobacco Survey (GATS) by the World Health Organization (WHO), which included the age at which one began smoking, the number of cigarettes smoked per day, the years of smoking, duration of smoking cessation, and so forth
In the subgroup of light smokers, we found that the gray matter (GM) of superior temporal gyrus (STG), insula, Middle occipital gyrus (MOG), posterior cingulate (PC), cerebellum anterior lobe (CAL), Caudate body (CB), and precuneus exhibited atrophy than non-smokers (Figure 3)
Summary
Smoking, which is one of the most critical and preventable causes of morbidity and mortality, has always been a thriving focus in research studies. A rising number of functional MRI studies have been conducted to examine the effects of acute nicotine intake between smokers and non-smokers, and a common finding is that, nicotine globally mitigates brain activities (Brody, 2006; Jasinska et al, 2014). The adverse effects of smoking on brain structural changes have received substantial focus (Durazzo et al, 2013; Fritz et al, 2014), with some interesting studies reporting outcomes in the relationships that exist between smoking and thickness or density of cerebral cortex (Yu et al, 2013; Karama et al, 2015; Li et al, 2015; Power et al, 2015). Changes caused by cigarette should be separately studied in whole-brain GM or WM. Only a few studies have explored the effects of tobacco on GM and WM separately (Ikram et al, 2008; Duriez et al, 2014; Wang et al, 2015)
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