Association Between Long-Term Exposure to Particulate Matter and Glycated Hemoglobin Levels: A Cohort Study from the Korean Genome and Epidemiology Study

Background: Ambient air pollution, particularly particulate matter (PM), has been linked to metabolic disorders, including diabetes. We evaluated associations between long-term exposure to coarse particulate matter (PM10) and fine particulate matter (PM2.5) and glycated hemoglobin (HbA1c) levels in a Korean population and assessed whether specific subgroups exhibited heightened susceptibility. Methods: We analyzed 6940 participants without diabetes from the Korean Genome and Epidemiology Study (KoGES) Ansan-Ansung cohort. Participants contributed 35,395 observations across a mean follow-up of 5.1 visits (2005–2017). Linear mixed models estimated associations between PM exposure and HbA1c while adjusting for covariates, including body mass index (BMI), time, and region. Subgroup analyses stratified by sex, age, BMI, region, education, smoking status, drinking status, and exercise. Results: Higher long-term PM10 exposure was associated with elevated HbA1c (β = 0.0347 per interquartile range IQR increase of 9.48 μg/m3; 95% CI: 0.0220, 0.0473; p < 0.001). PM2.5 showed a comparable positive association (β = 0.0166 per IQR of 8.67 μg/m3; 95% CI: 0.0010, 0.0321; p = 0.037). Associations were stronger among older adults (≥60 years: β = 0.0789 vs. <60 years: β = 0.0210; p-interaction < 0.001), rural Ansung residents (β = 0.0963 vs. Ansan: β = 0.0398; p-interaction < 0.001), participants with lower educational attainment (≤middle school: β = 0.0637; p-interaction < 0.001), and never smokers (β = 0.0455; p-interaction = 0.035). Conclusions: Among nondiabetic Korean adults, long-term PM10 exposure was associated with higher HbA1c; PM2.5 demonstrated a similar positive association. Associations were more pronounced among older adults, rural residents, individuals with lower educational attainment, and never smokers. These findings support ambient air pollution as an environmental contributor to subclinical glycemic changes and underscore the need for targeted public health strategies for vulnerable populations.