Air pollution, temperature, and HbA1c levels among children in Mexico City, Mexico

Glycated hemoglobin (HbA1c), a strong indicator of diabetes, is affected by air pollution and temperature exposures. However, studies examining the association between HbA1c, temperature, fine particulate matter (PM_2.5), and nitrogen dioxide (NO₂) among children are scarce, especially looking at all exposures simultaneously. We investigated the associations between these exposures and HbA1c among children, known to be a highly susceptible group. We included children enrolled in the Programming Research in Obesity, Growth, Environment, and Social Stressors (PROGRESS) cohort based in Mexico City (2013-2019). We obtained exposures from spatiotemporal models. HbA1c levels were measured at 4-5 years, 6-7 years, and 8-11 years post-birth. We used multivariable linear mixed-effects models to assess the simultaneous associations of three-month averages of PM_2.5, temperature, and NO₂ exposures with natural log-transformed HbA1c levels. We fitted stratified models by sex and age group. We included 1186 HbA1c measurements from 503 children. In multi-exposures models 1-µg/m³ increase in PM_2.5 was associated with 0.311 % (95 % CI:0.159, 0.464) relative increase in HbA1c and 1-degree Celsius increase in average temperature was associated with a -0.626 % (95 % CI: -0.977, -0.274) relative decrease. We did not find an association with a 1-ppb increase in NO₂ (-0.010 %. 95 % CI: -0.126, 0.106). The stratified analysis found slightly different associations by sex and age. This study adds evidence of HbA1c increases associated with lower temperatures and higher PM_2.5 exposure in an area with high air pollution and moderate temperature fluctuation. These glycemic changes may translate into increased diabetes risk in later life.