Interaction effects of exposure to air pollution and social activities on cognitive function in middle-aged and older Chinese adults based on a nationwide cohort study

Background: Although there have been many studies on the relationship between ambient air pollution and cognitive functioning in developed countries, there are no studies focusing on the interaction between ambient air pollution and social activities. This study aims to examine interactive effects of ambient air pollution and social activities on cognitive function in Chinese middle-aged and older.

Methods: This study used nationally representative longitudinal survey data of China Health and Retirement Longitudinal Study (CHARLS) 2013, 2015 and 2018. The study explored the additive interaction effects of air pollutants and social activities on cognitive function in middle-aged and older adults by constructing mixed linear regression analyses containing interaction terms, as well as constructing additive interaction analyses with dummy variables containing four unordered categories that were partitioned according to median. In addition, the study further explored the interaction between air pollution and different types of social activities through an interaction term between air pollution and different types of social activities.

Results: In the model fully adjusted for covariates such as age, sex, region, we found significant coefficients on the interaction term between PM_2.5, O₃ and social activities on cognitive function (PM_2.5, β = -0.018, 95%CI: -0.029, -0.006; O₃, β = 0.017, 95%CI: 0.007, 0.027). In the interaction analysis by constructing dummy variables, we found a significant antagonistic effect between PM_2.5 and social activities (SI = 0.730, 95%CI: 0.674, 0.785), a possible antagonistic effect between NO₂ and social activities (SI = 0.697, 95%CI: 0.648, 0.747), and a possible synergistic effect between O₃ and social activities (SI = 1.769, 95%CI: 0.648, 0.747). In addition, the study found significant interactions between simple interaction, leisure and recreational, and intellectual participation social activities and air pollution.

Conclusion: Our study demonstrated an antagonistic effect of PM_2.5 and social activities on cognitive function in middle-aged and older Chinese adults.