Comparison of Olfactory Disorders Between <scp>H1N1</scp> Influenza and <scp>COVID</scp> ‐19 Patients

ABSTRACT This study aimed to compare olfactory disorders (OD) and their risk factors in 497 H1N1 influenza patients and 369 COVID‐19 patients. Patients with H1N1 influenza and COVID‐19 were categorised into groups with and without OD using the Visual Analog Scale (VAS). The olfactory conditions and clinical characteristics of the group with OD among H1N1 influenza patients and COVID‐19 patients were compared, and the independent risk factors of OD were analysed. It was found that the incidence of OD in H1N1 influenza patients was 19.11%, lower than 25.75% observed in COVID‐19 patients ( χ 2 = 5.436, p = 0.020). Compared to COVID‐19 patients, the group with OD of H1N1 influenza patients showed a shorter overall disease course ( Z = −5.281, p &lt; 0.001), an earlier onset time of OD ( Z = −3.995, p &lt; 0.001), a shorter duration of OD ( Z = −8.816, p &lt; 0.001), as well as fewer comorbidities ( χ 2 = 4.456, p = 0.035). Age (OR = 1.021, p = 0.020), nasal symptoms (OR = 3.648, p &lt; 0.001), and smoking history (OR = 3.169, p = 0.002) were identified as independent risk factors for OD in H1N1 influenza patients, whereas nasal symptoms (OR = 4.466, p &lt; 0.001), comorbidities (OR = 3.861, p &lt; 0.001), and smoking history (OR = 2.129, p = 0.029) were independent risk factors for OD in COVID‐19 patients. H1N1 influenza patients were found to have a lower incidence, earlier onset, and faster recovery of OD, with different independent risk factors compared to COVID‐19 patients.