Relationship of smoking cessation duration and cognitive function among middle-aged and older adults in China: a national cross-sectional study

Background Population aging and smoking are both major challenges worldwide, particularly in developing countries. We preliminarily explored the relationship of smoking cessation duration and cognitive function among middle-aged and older Chinese.Methods The data comes from China Health and Retirement Longitudinal Study (CHARLS) wave 4. Smoking information was collected by standardized questionnaire. Global and memory-specific cognitive functions were assessed. We used restricted cubic spline to explore curvilinear relationship. After discretizing the duration of ex-smokers (quitting <= 2 years, 3-8 years, 9-19 years, and >= 20 years), multiple linear regression models were established with current smokers as reference.Results A total of 5,561 respondents (67.7 +/- 6.2 years; 54.1% men) were included. Respondents who quit smoking for longer showed better global cognitive function. This trend leveled off among respondents who had quit smoking for >= 20 years. There were significant differences in global cognitive function among those who quit smoking for >= 9 years (9-19 years, beta = 0.75, 95%CI 0.32-1.18; >= 20 years, beta = 0.94, 95%CI 0.42-1.46). The differences mainly came from men. In immediate memory, all ex-smokers performed better. In delayed memory, only those quit for >= 9 years had significant differences.Conclusion Compared with current smokers, both never smokers and ex-smokers showed better cognitive function. Respondents who quit smoking for longer had better cognitive performance, especially those who had quit for at least 9 years.