PURPOSE: Decreased olfactory and gustatory functions are present in various systemic autoimmune diseases. However, little is known about the chemosensory functions of patients with inflammatory bowel disease (IBD). The present study aimed to investigate olfactory and gustatory functions in patients with IBD and their correlation with clinical disease activity.

METHODS: A total of 103 patients with IBD were included (52 men, 51 women, mean age 40.3 ± 1.2 years) in the present study. Chemosensory functions were assessed utilizing the "Sniffin' Sticks" olfactory function test and "taste sprays" gustatory function test. The clinical disease activity of patients was graded as remission, mild, and moderate-severe. In addition, inflammatory markers (fecal calprotectin, C-reactive protein and blood leucocyte count) were recorded.

RESULTS: In total, 70% of IBD patients were normosmic, 30% were hyposmic, and none of them was functionally anosmic; 6% of the patients showed signs of hypogeusia. Patients with moderate-severe IBD reached a higher olfactory threshold score compared with patients with remission (p = 0.011) and mild IBD (p < 0.001). The BMI of IBD patients was inversely correlated with their olfactory threshold (r = -0.25, p = 0.010). Olfactory and gustatory function in IBD patients did not correlate with duration of disease, blood leucocyte count, CRP level, or fecal calprotectin level. However, patients' olfactory function significantly increased after 4 months of TNF-α inhibitor treatment (p = 0.038).

CONCLUSIONS: IBD patients are more likely to present with hyposmia. Olfactory thresholds were mainly affected. They were significantly associated with clinical disease activity and BMI. As shown in a subgroup, treatment with TNF-α inhibitors appeared to improve olfactory function.