Assessment of the difference in detection of pleasant and unpleasant odors in different grades of hyposmia

Abstract Background Olfaction is a complex process involving different neurological mechanisms with a correlation between the chemical structure and quality of odors regarding pleasantness. This study aimed to compare the detection of pleasant and unpleasant odors in different grades of hyposmia. A descriptive cross-sectional study was conducted preceded by a preliminary pilot study, including 20 normal subjects without a history of hyposmia. The pilot study was carried out using the University of Pennsylvania Smell Identification Test (UPSIT) with the assessment of pleasantness of odors using a visual analog scale (VAS). Fifty patients diagnosed with organic hyposmia/anosmia were included in the main study and assessed for the degree of hyposmia/anosmia using UPSIT. The number of detected odors out of the five odors with highest VAS for pleasantness and five odors with lowest VAS for pleasantness, as detected by the pilot study, for every patient was assessed and compared. Results There was a significant difference between the detection of pleasant and unpleasant odors in mild, moderate, and severe hyposmia (p value = 0.02, 0.005, and 0.03 respectively) with a highly significant difference in the whole study group ( p < 0.00001) with more loss of ability to detect unpleasant odors compared with pleasant odors. Conclusion The current study showed significantly less ability to detect unpleasant odors compared with pleasant odors in different grades of hyposmia. This finding suggests that the pattern of degeneration of the olfactory sense organ is not uniform with the topographic nature of the olfactory membrane.