Air pollution linked to metabolic and comorbidity markers in recent-onset diabetes

Researchers analyzed 1,120 people with recent-onset diabetes in the German Diabetes Study: 417 with type 1 and 703 with type 2 diabetes. They related five-year average residential exposure to PM2.5, PM10 and nitrogen dioxide to HbA1c, clamp-derived measures of insulin sensitivity and clearance, stimulated C-peptide, cardiovascular risk, cardiorespiratory fitness, albuminuria and distal sensorimotor polyneuropathy. The cross-sectional analysis used multivariable regression and included sensitivity analyses.

For each interquartile-range increase in PM2.5, type 2 diabetes was associated with higher HbA1c (exp[β] 1.04, 95% CI 1.01–1.06), lower insulin sensitivity and secretion, lower insulin clearance, reduced fitness, higher albuminuria and greater odds of polyneuropathy (OR 1.53, 95% CI 1.02–2.32). The cardiovascular risk estimate was higher but its confidence interval included 1. In type 1 diabetes, PM2.5 was associated with higher HbA1c and albuminuria, lower fitness, and higher insulin secretion. Similar patterns were reported for PM10 and nitrogen dioxide.

Associations were less consistent in type 1 diabetes and were attenuated in two-pollutant models. Because this was an observational, cross-sectional analysis, it cannot establish that pollution caused the differences or determine their direction over time. The findings do not establish a clinical intervention based on individual exposure.