Relationship between smoking and cognitive decline: a 4-year cohort prospective study on rural population in Xi'an

Objective This study examined the association between smoking and cognitive decline through a cohortinruralpopulationin Xi'an.Methods Data were collected from the cognitive impairment cohort of middleaged and elderly people in rural areas of Xi'an. The cohort selected the population aged 40 years and above in rural Xi'an. The baseline survey was completed between October 2014 and March 2015, and two follow-up visits were conducted in 2016 and 2018. This study took the baseline cognitively normal population of this cohort as the research subjects. According to the survey results in 2018, the population was divided into three groups according to smoking status:smoking, quitting and non-smoking. Cognitive function was assessed by Mini-Mental State Examination (MMSE). ΔMMSE (2014 rating-2018 rating) ≥2 was defined as cognitive decline, and ΔMMSE ＜2 was defined as cognitive stability. Binary Logistic regression model and stratified analysis were used to analyze the relationship between smoking and cognitive decline and the influence of age on the relationship. Results A total of 1289 subjects were included in this study. According to smoking status in 2018, they were divided into non-smokers (910, 70.6%), smokers (335, 26.0%), and ex-smokers (44, 3.4%). In the total population, there was no significant difference in the incidence of cognitive decline among non-smokers, smokers and ex-smokers (17.3%vs.16.1%vs.15.9%, P= 0.880).When stratified by age, there was no significant difference in the incidence of cognitive decline among the three groups in the subgroup of age ＜65 years (16.5%vs.13.2%vs.12.1%, P=0.365). In the subgroup of age ≥ 65 years, no significant difference was found in the incidence of cognitive decline among non-smokers, smokers and ex-smokers (20.8%vs.30.9%vs.27.3%, P=0.306).After adjusting for confounding factors, smokers had a significantly higher risk of cognitive decline than non-smokers (OR=14.139；95%CI ：1.541-129.705；P=0.019). There was a trend of cognitive decline in the ex-smokers group, but with no statistical significance (OR=8.252；95% CI ：0.630-108.175；P=0.108). Conclusion Smoking is positively associated with cognitive decline in the elderly, suggesting that smoking may accelerate cognitive decline in this population.