Effect of pollution on the prevalence of obesity, diabetic complications and olfactory dysfunction in diabetic patients

Purpose The aim of the study is to evaluate the effects of pollution on the prevalence of obesity, diabetic complications, and olfactory disfunction – OD (and their relationships) in two comparable groups of patients with type 2 diabetes (T2DM) living in different areas with different exposure to pollutants. Methods Two comparable groups of patients with T2DM coming from the 2 areas in the Lombardy region with the higher (Milan) and the lower (Sondrio) level of pollution in the past 10 years were analyzed. Each patient underwent a diabetologic, ophthalmologic, cardiologic and otorhinolaryngologic examination which also included the assessment of olfactory abilities and olfactory-related quality of life (QoL). Statistical analysis used non-parametric tests and logistic regression. Results The prevalence of diabetic complications and OD was significantly higher in patients from Milan than from Sondrio (p=0.007 and p=0.039 at Fisher test, respectively), while no significant difference was found for obesity (p=0.716 at Fisher test). The group with a greater prevalence of OD also reported worse olfactory-related QoL (p=0.001 and p=0.016 at Fishertest respectively for Biref-IT-QOD-P and Biref-IT-QOD-NS, respectively). Regression analysis showed a significant association between OD and the presence of diabetic complications (p=0.011 at multivariable analysis), and between complications and diabetes duration (p=0.001 at multivariable analysis). Pollution exposure was a weak independent predictor for both OD and complications in patients with T2DM. Conclusion Our study showed that patients with T2DM subject to a higher exposure to pollution were more frequently affected by diabetic complications and OD and reported a poorer olfactory-related QoL compared to patients with a lower exposure. We were also able to highlight a strong association between OD and T2DM complications.