Epidemiology of Anosmia in South Korea: A Nationwide Population-Based Study

Abstract

Research about the epidemiology of olfactory dysfunction in Asians was not enough. the purpose of this study was to assess the prevalence and incidence rate of olfactory disorders in Koreans and to evaluate demographic risk factors. We analyzed clinical data of patients with anosmia using Korean National Health Insurance Service data from 2006 to 2016. The data includes medical insurance claim data and medical records of almost 50,000,000 people in Korea. The 30-39 age group showed the highest prevalence (19.25 per 10,000 per year). Their incidence rate was also high comparing other age groups (13.30 per 10,000 per year). The prevalence and the incidence increased from 7.10 to 13.74 and from 5.66 to 9.54 between 2006 and 2016. In the seasonal analysis, the incidence rate was high in spring and autumn. The high-income population showed about 1.4-folds higher incidence rate than the lowincome population. We thought that the socioeconomic status could generally affect the rate of hospital visit in the anosmia population. Anosmia can be frequently underdiagnosed in the clinical environment because the elderly and the low-income people easily underestimate their anosmia symptom and ignore the severity due to their economic problem. therefore careful attention and further studies for anosmia are needed. Olfaction is the sense of smell that chemically detects odorants in the air. Perhaps the most crucial function of olfaction is an early warning system for the detection of fire, leaking of natural gas, contaminated air, and spoiled food 1-4. It also has functions to determine the flavor and palatability of foods and drinks 1,4. Despite many roles of olfaction, it is regarded less importantly compared to vision or hearing 1. Another important reason why the importance of olfactory disorder is overlooked is that we cannot easily detect olfactory depletion 1,5. Young patients with congenital olfactory disorders show tend not to aware of olfactory disturbances of their own 5. So far, there is no standardized diagnostic method for anosmia. Although olfactory event-related potentials (OERPs) and electro-olfactogram (EOG) can be used to objectively measure olfactory function, they have many limitations to be used as an objective diagnostic method until now. For these reasons, psychophysical tests are quite commonly used, such as the University of Pennsylvania Smell Identification Test (UPSIT) or Sniffin' Sticks 6-9. UPSIT was developed by American and Sniffin's Sticks test was invented by Germany G. Kobal. UPSIT contains odors in 40 microencapsulations, which are then scratched with a pen and sniffed to identify odors, then identifying the olfactory status by percentiles according to age and gender. UPSIT, however, has a lot of smells that are not familiar to Koreans, and because of the one-time use, it is expensive and involves only an identification test. Therefore, in Korea, Korean Version of Sniffin' Sticks Test (KVSS), which is inexpensive and can be repeatedly conducted, has been developed and used for the diagnosis of a...

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