Multi-angles of smoking and mild cognitive impairment: is the association mediated by sleep duration?

Although the association between cigarette smoking and risk of mild cognitive impairment (MCI) is controversial, most recent studies have shown that this influence is negative. However, it is unknown how multiple factors of smoking affect MCI, and the mechanisms of different smoking factors are not yet clarified. This study will examine the impact of various angles of smoking on MCI and the potential mediating effects of sleep duration on smoking MCI association in the elderly. In the case group, 109 elderly people who met the inclusion criteria were selected, and 123 were selected in the control group. Participant characteristics include sleep duration and a detailed lifetime history of smoking. After adjusting the relevant covariates, higher odds of MCI occurrence were found in ex-smokers/current smokers; moderate/heavy smokers; smokers for 30–44, 45–59 and more than 60 years; smokers with cumulative smoking duration of 30–44 or more than 60 years and smokers with cumulative dose smoking intensity of 200–399 or 400–599 cigarettes monthly. Elderly subjects who had quit smoking for 21 years or longer were found to have lower odds of MCI occurrence. The indirect effects of smoking on MCI via sleep duration were statistically significant, as the ratio of indirect effect to total effect ranged from 0.14 to 0.29. Smoking affects cognitive function through multi-angles of smoking and influences the cognitive function partly via the duration of sleep.