Evaluation of olfaction and taste function in type 2 diabetic patients with and without peripheral neuropathy

Previous studies reported that the taste disorder is a common observation in diabetes mellitus (DM) with a significant and somewhat specific impairment in sweet taste detection. The results of these studies are contradictory in some aspects, thus suggesting the need for further evaluative studies. Therefore, the author conducted this study to demonstrates that T2DM is associated with olfactory and gustatory dysfunction.

Among patients with diabetes mellitus, gustation and olfaction play a significant impact on quality of life, and their impairment may end in possible hazards. The studies involved the assessment of gustatory and olfactory function alteration among the type 2 diabetic patients with diabetic peripheral neuropathy (DPN) were minimal. This study aimed to define the incidence of major olfactory and gustatory dysfunction among type 2 diabetic patients with or without DPN using approved and reliable approaches.

A total of 60 type 2 diabetic patients and 30 healthy patients with 57.1±8.4 mean age were selected for an observational-analytical case-control study. After clinical assessment and electromyography analysis, T2DM patients were classified into the two groups; with and without DPN. The blood samples for the serum creatinine, lipids, and HbA1c measurement were taken after a 10-hour fasting period. All subjects went through odour identification test and butanol threshold test to assess olfactory function quantitatively. A whole-mouth above-threshold test using sucrose solutions was administrated to examine the gustatory function.  

A significant higher Sniffin' sticks and butanol threshold scores were noticed among the control subjects as compared to diabetic patients without DPN. The gustatory function test found to be similar among both groups. Higher sucrose thresholds, lower butanol threshold scores, and Sniffin' sticks scores were showed by the diabetic patients with DPN as compared to controls. No difference was seen regarding butanol threshold, sucrose thresholds, and Sniffin' sticks scores between diabetic patients with or without DPN.  

As per findings, the T2DM show a significant association with gustatory and olfactory dysfunction. The similarity between the groups evokes the idea of central neuropathy. This conclusion might facilitate the involvement of gustatory and olfactory tests to the methodological spectrum of afferent pathway examinations.