Early risk detection and management are essential for cognitive preservation. While particulate matters of diameter small than 2.5 μm (PM2.5) is considered harmful to cognition, the effect of smaller, more penetrative particulate matters of diameter small than 1 μm (PM1) requires further evidence and explicit safety thresholds. In this study, we explored the effects of long-term PM1 exposure on early cognitive impairment and longitudinal cognitive changes in middle-aged and older populations. This study assessed data from two large-scale longitudinal surveys: the China Health and Retirement Longitudinal Study (CHARLS) and UK Biobank (UKB). Cross-sectional, longitudinal, and trajectory analyses were conducted to investigate the association between long-term PM1 exposure and cognition. Additionally, the exposure–response curves were fitted to determine the customized thresholds. The findings indicated that sustained PM1 exposure may lead to mild cognitive impairment, particularly at concentrations exceeding 30 and 5.6 μg·m−3 in CHARLS and UKB participants, respectively. Furthermore, we found that long-term PM1 exposure can contribute to rapid cognitive decline at concentrations exceeding 23 and 5.5 μg·m−3 in CHARLS and UKB participants, respectively. In conclusion, reducing PM1 exposure can improve the cognitive health of middle-aged and older adults.

Early risk detection and management are essential for cognitive preservation. While particulate matter with a diameter smaller than 2.5 μm (PM_2.5) is considered harmful to cognition, the effect of smaller, more penetrative particulate matter with a diameter smaller than 1 μm (PM₁) requires further evidence and explicit safety thresholds. In this study, we explored the effects of long-term PM₁ exposure on early cognitive impairment and longitudinal cognitive changes in middle-aged and older populations. This study assessed data from two large-scale longitudinal surveys: the China Health and Retirement Longitudinal Study (CHARLS) and UK Biobank (UKB). Cross-sectional, longitudinal, and trajectory analyses were conducted to investigate the association between long-term PM₁ exposure and cognition. Additionally, the exposure–response curves were fitted to determine the customized thresholds. The findings indicated that sustained PM₁ exposure may lead to mild cognitive impairment, particularly at concentrations exceeding 30 and 5.6 μg·m⁻³ in CHARLS and UKB participants, respectively. Furthermore, we found that long-term PM₁ exposure can contribute to rapid cognitive decline at concentrations exceeding 23 and 5.5 μg·m⁻³ in CHARLS and UKB participants, respectively. In conclusion, reducing PM₁ exposure can improve the cognitive health of middle-aged and older adults.