Abstract
OBJECTIVE: The purpose of the study is to compare the prevalence and associated risk factors of smell and/or taste disorders depending on different virus strains in Hiroshima, Japan. DESIGN: A cross-sectional design was used. SETTING AND PARTICIPANTS: Data were collected for all COVID-19-confirmed inpatients admitted to 27 hospitals in Hiroshima prefecture, Japan, between 8 April 2020 and 31 January 2023. MAIN OUTCOME MEASURES: Smell and/or taste disorders were indicated by physicians on Hiroshima prefecture COVID-19 version J-SPEED forms completed at discharge. RESULTS: The COVID-19 data from this period corresponds to the following four strains: Wild-dominant, Alpha-dominant, Delta-dominant and Omicron-dominant. A total of 11 353 confirmed cases were analysed and 1261 cases (11.11%) were reported for smell and/or taste disorders.Among patients with Wild-dominant, 241 out of 1141 cases (21.12%) exhibited smell and/or taste disorders. For Alpha, 223 out of 1265 cases (17.63%), for Delta, 480 out of 1516 cases (31.66%) and for Omicron, 317 out of 7431 cases (4.27%) presented with smell and/or taste disorders. For all four variants, age<65 (Wild: adjusted odds ratio [aOR]=2.66, 95% confidence interval [CI]:1.82-3.88; Alpha:aOR=2.00, 95%CI:1.39-2.88; Delta: aOR=2.42, 95%CI:1.54-3.81; Omicron: aOR=1.84, 95%CI:1.40-2.42) were related to smell and/or taste disorders. For the Wild and Delta variants, higher odds of reporting smell and/or taste disorders were found among wmen (Wild:aOR=1.63, 95%CI:1.20-2.22; Delta: aOR=1.41, 95%CI:1.10- 1.80). CONCLUSIONS: The proportion of patients with smell and/or taste disorders varied significantly depending on the virus strain. Our findings indicate that the Delta-dominant period had the highest number of patients with these disorders, while the Omicron-dominant period had the lowest. Moreover, our study identified risk factors for smell and/or taste disorders for each variant.