Long-term exposure to ambient PM2.5 constituents and risk of microvascular complications among individuals with type 2 diabetes mellitus: a nationwide cohort study in UK.

This study aimed to investigate the associations of long-term exposure to PM2.5 constituents with microvascular complications among participants with T2DM. This prospective study involved 27,579 participants with T2D without microvascular complications at baseline from the UK Biobank. PM2.5 and its five main constituents, including elemental carbon (EC), organic matter (OM), ammonium (NH4+), nitrate (NO3-), and sulfate (SO42-) were estimated were estimated using EMEP4UK-WRF model meteorology. Quantile g-computation (QgC) approach was applied to estimate the joint effect of PM2.5 constituents and identify which constituents contribute most to it. In the multivariate-adjusted model, increased exposure levels for PM2.5 constituents were significantly associated with increased risk of diabetic microvascular complications among individuals with T2DM. In detail, per IQR increment in PM2.5 (HR = 1.09, 95% CI: 1.06-1.14), EC (HR = 1.06, 95% CI: 1.02-1.10), OM (HR = 1.05, 95% CI: 1.01-1.09), NH4+ (HR = 1.15, 95% CI: 1.10-1.21), NO3- (HR = 1.10, 95% CI: 1.07-1.13), and SO42- (HR = 1.13, 95% CI: 1.07-1.19) was significantly associated with a higher risk of diabetic microvascular complications. Similar associations were observed for diabetic neuropathy, nephropathy, and retinopathy. The QgC methods showed that the mixed constituents were positively associated with microvascular complications (HR = 1.59, 95% CI: 1.54-1.64, P < 0.001) and specific subtypes. The constituent with the largest estimated positive weight was SO42-, followed by NH4+ and EC. In summary, long-term exposure to PM2.5 constituents with an increased risk of diabetic microvascular complications among participants with T2DM. Importantly, SO42- might take primary responsibility for these relationships.