Comparison of The Salty Taste Test Results, The Olfactory Test Results, and Questionnaire Survey Results before the COVID-19 Epidemic (2019) and after the COVID-19 Epidemic (2022) in The Medical Examination for Residents of Yakumo Town, Hokkaido, Japan in the Same 100 Participants

Abstract

Since 2005, we have conducted a questionnaire survey on taste and olfaction, the salty taste test, and the olfactory test in Yakumo Town, Hokkaido, Japan. However, due to the COVID-19 epidemic, resident screening was canceled in 2020 and 2021. We investigated the potential impact of COVID-19 by comparing results from the salty taste test, olfactory tests, and questionnaire surveys. Data were analyzed for a total of 100 individuals, 42 males, and 58 females, who underwent screening in both 2019 and 2022. The questionnaire survey included items regarding the subjective presence or absence of dizziness, tinnitus, headache, taste, smell, and saliva secretion. Furthermore, we obtained results from a salty taste test using the Solsave kit (manufactured by Advantech) and olfactory test results using the smell stick kit (manufactured by Daiichi Kogyo Co., Ltd.). Consequently, when comparing the results of the olfactory test between 2019 and 2022 for 42 males, a statistically significant difference (p = 0.004) emerged. The ability to understand odors was more challenging in 2022 compared to 2019. Specifically, distinguishing between the odors of perfume (p = 0.044), menthol (p = 0.032), mandarin orange (p = 0.032), and fried garlic (p = 0.019) proved to be difficult. Similarly, in the comparison of 2019 and 2022 for 58 females, there was a statistically significant difference (p = 0.033) in olfactory test results, indicating that comprehending odors was more difficult in 2022 than in 2019. Particularly, distinguishing between the odors of perfume (p = 0.026), mandarin orange (p = 0.026), and condensed milk (p = 0.018) presented challenges. There was no statistically significant difference in the results of the salty taste test and questionnaire survey for both males and females. To determine whether the observed changes in olfactory sense are due to aging changes over the three years or the effects of COVID-19, ongoing investigation is crucial. It is necessary to continue assessing whether this diminished sense of smell will recover in the future.