Decreased Central Nervous System Grey Matter Volume (GMV) in Smokers Affects Cognitive Abilities: A Systematic Review

Although cigarette smoking is a leading cause of preventable mortality, tobacco is consumed by approximately 22% of the adult population worldwide. Smoking is also a risk factor for cardiovascular disease, affects brain processing, and is a recognized risk factor for Alzheimer disease (AD). Tobacco toxins (e.g., nicotine at high levels) inhaled in smoke may cause disorders resulting in preclinical brain changes. Researchers suggest that there are differences in brain volume between smokers and non-smokers. This review examines these differences in brain grey matter volume (GMV). In March/April 2015, MedLine, Embase, and PsycINFO were searched using the terms: “grey matter” AND “voxel-based” AND “smoking” AND “cigarette”. The 4 studies analyzed found brain GMV decreases in smokers compared to non-smokers. Furthermore, sex-specific differences were found; while the thalamus and cerebellum were affected in both sexes, decreased GMV in the 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 1 study found a positive correlation between number of pack-years smoked and GMV. Smoking decreases GMV in most brain areas. This decrease may be responsible for the cognitive impairment and difficulties with emotional regulation found in smokers compared with non-smokers.