Differences in taste and smell perception between type 2 diabetes mellitus patients and healthy controls

Background and Aims: Taste and smell senses are essential determinants of food choice which, in turn, may contribute to the development of chronic diseases, including diabetes. Although past studies have evaluated the relationship between type 2 diabetes mellitus (DM2) and senses disorders, this relationship still remains controversial. In this study, we evaluated taste and smell perception in DM2 patients and healthy controls (HC). Moreover, in DM2 patients we analyzed the association of chemosensory impairments with anthropometric and clinical outcomes (e.g. Body Mass Index (BMI), Fasting blood glucose (FBG), drugs, cardiovascular diseases (CVD) and hypertension). Methods and Results: The study included 94 DM2 patients and 244 HC. Taste recognition for 6-n-propylthiouracil (PROP), quinine, citric acid, sucrose and sodium chloride (NaCl) compounds was assessed using a filter paper method, while smell recognition of 12 odorants was performed using a sniffing sticks test. We found that a higher percentage of DM2 patients showed identification impairment in salt taste (22% vs. 5%, p-value<0.0009) and smell recognition (55% vs. 27%, p-value=0.03) compared to HC. We also observed that 65% of hypertensive DM2 subjects presented smell identification impairment respect to 18% of non-hypertensive patients (p-value=0.019). Finally, patients with impairments in both taste and smell showed elevated FBG compared to patients without impairment (149.6 vs.124.3 mg/dL, p-value=0.04). Conclusion: The prevalence of taste and smell identification impairments was higher in DM2 patients compared with HC and a possible relationship with glycemic levels emerged.