Faster olfactory adaptation in patients with olfactory deficits: an analysis of results from odor threshold testing.

BACKGROUND: Patients with olfactory deficits often report rapid and lasting olfactory adaptation compared to the time when they had normal olfactory function. However, this phenomenon receives little scientific attention. This retrospective study aimed to compare the patterns of olfactory adaptation in normosmic controls and patients with olfactory impairment by analyzing the trajectory of turning points in odor threshold tests based on the staircase technique. METHODS: 4120 subjects (1684 hyposmia, 1742 anosmia and 694 normosmic controls) were included in this study. Their odor threshold, odor discrimination and odor identification ability were assessed using the Sniffin’ Sticks. We analyzed the trajectory of turning points in the odor threshold test. RESULTS: Current results suggested that patients with hyposmia needed significantly more trials to reach the final threshold scores than controls and anosmic group, and controls needed more trials than anosmic group. The difference between the first turning point and final threshold scores in the anosmic group was significantly larger than in the hyposmia group and in controls. CONCLUSION: People with poor olfaction seem to adapt faster to olfactory stimuli. The trajectory of turning points in odor threshold test may serve as an indicator of olfactory adaptation and function of olfactory receptors. Olfactory adaptation may provide a new tool in the assessment of subtle olfactory loss.

The effect of olfactory training on olfactory bulb volumes in patients with idiopathic olfactory loss.

Olfactory loss impacts around 20% of the population and is associated with the reduction of pleasure from eating and drinking, sex and depression (1). Encouragingly, research findings have consistently demonstrated that olfactory training (OT) can improve olfactory function in people with olfactory loss due to various aetiologies (2). The most commonly used method for OT involves smelling four different odours (lemon, eucalyptus, rose and cloves), twice daily, for 12 weeks.