Insulin resistance and the increased risk for smell dysfunction in US adults

Over 24% of older American adults (approximately 14 million) are estimated to have reduced olfactory sensitivity. Previous studies have provided evidence that patients with diabetes mellitus (DM) or its complications are at increased risk of olfactory dysfunction. We therefore investigated whether smell dysfunction was associated with DM-related biomarkers, including fasting blood glucose, glycohemoglobin, serum insulin, and homeostasis model assessment of insulin sensitivity (HOMA-IR), in older US adults.

Data from 9,678 older adults who had participated in the 2013 to 2014 National Health and Nutrition Examination Survey were available for this study. We used the eight-item, self-administered scratch-and-sniff smell test (Sensonics, Inc., Haddon Heights, NJ) for assessing smell. Smell dysfunction was defined as the condition with an odor identification score of ≤ 5.

Of the 978 participants, 20% of older adults (n = 193) were defined as having smell dysfunction. After adjustment for potential confounding variables, participants in the highest HOMA-IR quintile had approximately two-fold increased odds (odds ratio = 2.25; 95% confidence interval: 1.25-4.05) of smell dysfunction compared with those in the lowest HOMA-IR quintile. In contrast, the odds of smell dysfunction were not associated with the quintiles for fasting blood glucose, glycohemoglobin (HbA1c), or serum insulin levels.

We found a significant association between smell dysfunction and severe insulin resistance in older US adults. Our data suggests that insulin resistance may be mechanistically linked to loss of smell function.

4. Laryngoscope, 128:1992-1996, 2018.