Associations between air pollution and temperature on glycated hemoglobin levels in women of child bearing age

Abstract

BACKGROUND AND AIM: Fine particulate matter (PM₂.₅) is associated with cardiovascular disease possibly through impaired glucose metabolism. Higher temperature has been linked to lower blood glucose levels in clinical settings as well. We examined the association between intermediate-term exposure to PM₂.₅ and temperature and glycated hemoglobin (HbA1c), a longer-term marker of glucose control. METHODS: We assessed air pollution and temperature at 1-km² spatial resolution via satellite-based models, and HbA1c four years postpartum in women enrolled in the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) cohort in Mexico City (2013–2019). PM₂.₅ and temperature were matched to participants’ addresses and confirmed by GPS tracker. Using linear mixed-effects models, we examined the association between 3-month and 6-month average PM₂.₅ and temperature with log-transformed HbA1c values. Both models included a random intercept per woman and were adjusted for calendar year, season, and individual-level confounders (age, marital status, smoking status, alcohol consumption level, and education level). RESULTS:We analyzed 1,257 tests of 490 women. PM₂.₅ ranged from 3.2µg/m³ to 76.7µg/m³, average temperature ranged from 6.4°C to 22.9°C, and HbA1c values ranged from 3.0% to 12.8%. Results were antilog transformed and are presented as percent increases in HbA1c levels. Per interquartile increase in 3-month and 6-month average PM₂.₅, HbA1c levels increased by 1.85% (95%CI: 0.92, 2.80) and 1.08% (95%CI: 0.10%, 2.08%) respectively. Per one-degree Celsius increase in temperature, HbA1c levels decreased by 0.64% (95%CI: -1.05%, -0.23%) and 0.58% (95%CI: -1.04%, -0.12%) respectively. CONCLUSIONS:Intermediate-term exposure to PM₂.₅ and temperature are associated with opposing changes in HbA1c levels, in this region of high PM₂.₅ and moderate temperature fluctuation. These effects, measurable in mid-adult life, may portend future risk of heart disease and type 2 diabetes. Additional research is necessary to elucidate whether the observed associations with HbA1c mediate early indicators of cardiovascular disease as the cohort ages. KEYWORDS: air pollution, particulate matter, temperature, diabetes, glycated hemoglobin, HbA1c