Interactions between cigarette smoking and cognitive status on functional connectivity of the cortico-striatal circuits in individuals without dementia: A resting-state functional MRI study

Aims Cigarette smoking is a modifiable risk factor for Alzheimer's disease (AD), and controlling risk factors may curb the progression of AD. However, the underlying neural mechanisms of the effects of smoking on cognition remain largely unclear. Therefore, we aimed to explore the interaction effects of smoking x cognitive status on cortico-striatal circuits, which play a crucial role in addiction and cognition, in individuals without dementia. Methods We enrolled 304 cognitively normal (CN) non-smokers, 44 CN smokers, 130 mild cognitive impairment (MCI) non-smokers, and 33 MCI smokers. The mixed-effect analysis was performed to explore the interaction effects between smoking and cognitive status (CN vs. MCI) based on functional connectivity (FC) of the striatal subregions (caudate, putamen, and nucleus accumbens [NAc]). Results The significant interaction effects of smoking x cognitive status on FC of the striatal subregions were detected in the left inferior parietal lobule (IPL), bilateral cuneus, and bilateral anterior cingulate cortex (ACC). Specifically, increased FC of right caudate to left IPL was found in CN smokers compared with non-smokers. The MCI smokers showed decreased FC of right caudate to left IPL and of right putamen to bilateral cuneus and increased FC of bilateral NAc to bilateral ACC compared with CN smokers and MCI non-smokers. Furthermore, a positive correlation between FC of the NAc to ACC with language and memory was detected in MCI smokers. Conclusions Cigarette smoking could affect the function of cortico-striatal circuits in patients with MCI. Our findings suggest that quitting smoking in the prodromal stage of AD may have the potential to prevent disease progression.