A Life Without Smell: Olfactory Function in People Working in Odorless Rooms

OBJECTIVES

Odorous stimulation helps to maintain or to improve olfactory function. In contrast, odor deprivation has been suggested to facilitate olfactory impairment. The aim of this study was to investigate the effects of odor deprivation in people working in an odorless environment.

METHODS

Fifty people working in an odorless environment for extended periods of time and 50 people not working in such environments were recruited. The participants were examined for olfactory function (using Sniffin' Sticks), nasal airflow (using peak nasal inspiratory flowmetry), self-rated olfactory function, self-rated nasal airflow, and well-being. Correlation analyses were used to explore the associations between the duration of working in odorless environment and olfaction, nasal airflow, and well-being.

RESULTS

The cleanroom workers exhibited slightly, but significantly reduced olfactory scores (sensitivity 7.0 ± 2.5, discrimination 11.4 ± 1.8) compared with controls (sensitivity 8.9 ± 2.5, F = 4.33, p = 0.03; discrimination 12.7 ± 1.6. F = 5.50, p = 0.001), even when controlling for age and rated nasal patency, with their self-rated olfactory function being not affected. The years of working in cleanrooms were negatively associated with olfactory function (r = 0.35, p = 0.013). No significant correlations were observed between scores of olfactory function, nasal patency, and well-being.

CONCLUSION

Compared with controls cleanroom workers exhibited slightly, but significantly lower olfactory scores, nasal peak flow, and well-being. Their decreased odor sensitivity was found to be associated with the number of years they had worked in the cleanroom. Overall, these results may suggest that odorous stimulation supports olfactory functioning.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:382-387, 2024.

Nasal airflow engages central olfactory processing and shapes olfactory percepts

Binding of airborne odour molecules to olfactory receptors at the top of the nasal cavity gives rise to our rich olfactory experience. Whether airflow plays a role in human olfactory perception beyond the transportation of odorants is scantly known. Combining psychophysical measures with strict controls of nasal flow parameters, we demonstrate in four experiments that the perceived intensity of a unilaterally presented odour decreases systematically with the amount of contralateral nasal airflow, in manners that are independent of odour flow rate, nasal pressure, perceived sniff vigour or attentional allocation. Moreover, the effect is due to the sensed rather than the factual amount of nasal flow, as applying a local anaesthetic to the contralateral nostril produces the same effect as physically blocking it. Our findings indicate that nasal flow spontaneously engages central olfactory processing and serves as an integral part of the olfactory percept in humans.