Anosmia is associated with lower in-hospital mortality in COVID-19

Background: Anosmia is common in Coronavirus disease 2019, but its impact on prognosis is unknown. We analysed whether anosmia predicts in-hospital mortality; and if patients with anosmia have a different clinical presentation, inflammatory response, or disease severity. Methods: Retrospective cohort study including all consecutive hospitalized patients with confirmed Covid-19 from March 8th to April 11th, 2020. We determined all-cause mortality and need of intensive care unit (ICU) admission. We registered the first and worst laboratory parameters. Statistical analysis was done by multivariate logistic and linear regression. Results: We included 576 patients, 43.3% female, and aged 67.2 years in mean. Anosmia was present in 146 (25.3%) patients. Patients with anosmia were more frequently females, younger and less disabled and had less frequently hypertension, diabetes, smoking habit, cardiac and neurological comorbidities. Anosmia was independently associated with lower mortality (OR: 0.180, 95% CI: 0.069-0.472) and ICU admission (OR: 0.438, 95% CI: 0.229-0.838, p = 0.013). In the multivariate analysis, patients with anosmia had a higher frequency of cough (OR: 1.96, 95%CI: 1.18-3.28), headache (OR: 2.58, 95% CI: 1.66-4.03), and myalgia (OR: 1.74, 95% CI: 1.12-2.71). They had higher adjusted values of hemoglobin (+0.87, 95% CI: 0.40-1.34), lymphocytes (+849.24, 95% CI: 157.45-1541.04), glomerular filtration rate (+6.42, 95% CI: 2.14-10.71), and lower D-dimer (-4886.52, 95% CI: -8655.29-(-1117.75)), and C-reactive protein (-24.92, 95% CI: -47.35-(-2.48)). Conclusions: Hospitalized Covid-19 patients with anosmia had a lower adjusted mortality rate and less severe course of the disease. This could be related to a distinct clinical presentation and a different inflammatory response.