Central nervous system grey matter decreases in volume in smokers impacting cognitive abilities: A systematic review

Background Even though cigarette smoking is a leading cause of preventable mortality, worldwide tobacco is consumed by approximately 22% of population. Smoking is also one of the risk factors for cardiovascular disease and it impacts our brain processing as well as being one of the recognised risk factors for Alzheimer's disease. The tobacco toxins may cause these disorders, e.g., nicotine at high levels, which are inhaled, resulting in preclinical brain changes. Researchers suggest that there are differences in brain volume between smokers and non-smokers. This review examines these differences on the brain grey matter volume (GMV). Material/methods In March/April 2015: MedLine, Embasse and PsycInfo were searched using terms: “grey matter”, “voxel based”, “smoking” and “cigarette”. Results Studies found brain GMV decreases in smokers compared to non-smokers. Furthermore, gender specific differences were found, while thalamus and cerebellum was affected in both genders decrease in olfactory gyrus was found only in male smokers. Age group differences were also found and these may suggest pre-existing abnormalities that lead to nicotine dependence in younger individuals. Only one study found positive correlation between number of pack-years and GMV. Conclusion Smoking decreases the volume of grey matter in most brain areas. This decrease may be responsible for the cognitive impairment and difficulties with emotional regulation in smokers compared with non-smokers.