Lifetime cigarette smoking is associated with striatal volume measures

Nicotine, the primary addictive component of tobacco, affects the mammalian brain. Smokers' brains have smaller cortical grey matter volumes and/or lower densities compared with non-smokers'. Differences in subcortical structures like the striatum are however, less clear. A high concentration of nicotinic receptors makes the striatum a potential target for nicotine. In addition, striatal nuclei are essential components of the reward/reinforcement pathway involved in addiction. The aim of this study was to explore the relationship between striatal nuclei (caudate, putamen and nucleus accumbens area) volumes and lifetime smoking in a large community-based sample of 'young-old' individuals. Brain volumes were measured using a semi-automated method in 315 participants aged 64-70 years who were selected from a larger randomly sampled cohort and who consented to a magnetic resonance imaging scan. Multiple regression analysis was used to assess the relationship between striatal volumes and cigarette smoking measures while controlling for age, sex, intracranial and total brain volumes and general physical and mental health measures. Greater lifetime use of cigarettes (measured in pack-years) was associated with smaller left nucleus accumbens area volume (P = 0.018) and larger left putamen volume (P = 0.025). Greater putaminal volume was also associated with a lower age at smoking initiation (P = 0.004). In this generally healthy cohort, lifetime use of cigarettes is significantly associated with striatal volume measures. These changes could indicate predisposing factors for nicotine addiction, or an effect of chronic nicotine exposure or a combination of both.