Systemic inflammation as a moderator of air pollution-associated self-reported health in middle-aged and older Chinese adults: evidence from a nationwide study

Prolonged exposure to air pollution and systemic inflammation has both been associated with deteriorating self-reported health (SRH), however, the underlying mechanisms remained poorly understood. This study included 8,292 middle-aged and older adults (≥45 years) from the China Health and Retirement Longitudinal Study (CHARLS). High spatial-temporal gridded air pollution datasets were utilized to estimate individual air pollution exposure at county level. Systemic inflammation was measured using C-reactive protein (CRP) and white blood cell (WBC) numbers from CHARLS blood samples. Generalized linear modeling (GLM) was employed to examine the relationships between air pollution exposure, systemic inflammation, and SRH. After adjusting for confounders, this study found that a 3-year average PM2.5 concentration was associated with a higher risk of poor SRH (OR = 1.005, 95% CI: 1.002-1.009). Elevated CRP and WBC levels were also linked to an increased risk of poor SRH (OR = 1.019, 95% CI: 1.011-1.027; OR = 1.035, 95% CI: 1.010-1.061, respectively). Interaction analysis revealed that elevated CRP levels exacerbated the adverse effect of chronic air pollution exposure on SRH. In addition, residential location and educational attainment influenced how systemic inflammation moderated the relationship between PM2.5 exposure and SRH. Long-term exposure to air pollution was associated with an increased likelihood of poor SRH among middle-aged and older adults, with inflammatory markers potentially amplifying this association. Therefore, it is essential to implement multidisciplinary strategies to reduce air pollution and alleviate systemic inflammation in this population.