Clinical Characteristics and Risk Factors of Respiratory Failure in a Cohort of Young Patients Requiring Hospital Admission with SARS-CoV2 Infection in Spain: Results of the Multicenter SEMI-COVID-19 Registry

Background Age is a risk factor for COVID severity. Most studies performed in hospitalized patients with SARS-CoV2 infection have shown an over-representation of older patients and consequently few have properly defined COVID-19 in younger patients who require hospital admission. The aim of the present study was to analyze the clinical characteristics and risk factors for the development of respiratory failure among young (18 to 50 years) hospitalized patients with COVID-19. Methods This retrospective nationwide cohort study included hospitalized patients from 18 to 50 years old with confirmed COVID-19 between March 1, 2020, and July 2, 2020. All patient data were obtained from the SEMI-COVID Registry. Respiratory failure was defined as the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (PaO2/FiO2 ratio) ≤200 mmHg or the need for mechanical ventilation and/or high-flow nasal cannula or the presence of acute respiratory distress syndrome. Results During the recruitment period, 15,034 patients were included in the SEMI-COVID-19 Registry, of whom 2327 (15.4%) were younger than 50 years. Respiratory failure developed in 343 (14.7%), while mortality occurred in 2.3%. Patients with respiratory failure showed a higher incidence of major adverse cardiac events (44 (13%) vs 14 (0.8%), p <0.001), venous thrombosis (23 (6.7%) vs 14 (0.8%), p <0.001), mortality (43 (12.5%) vs 7 (0.4%), p <0.001), and longer hospital stay (15 (9–24) vs 6 (4–9), p <0.001), than the remaining patients. In multivariate analysis, variables associated with the development of respiratory failure were obesity (odds ratio (OR), 2.42; 95% confidence interval (95% CI), 1.71 to 3.43; p <0.0001), alcohol abuse (OR, 2.40; 95% CI, 1.26 to 4.58; p =0.0076), sleep apnea syndrome (SAHS) (OR, 2.22; 95% CI, 1.07 to 3.43; p =0.032), Charlson index ≥1 (OR, 1.77; 95% CI, 1.25 to 2.52; p =0.0013), fever (OR, 1.58; 95% CI, 1.13 to 2.22; p =0.0075), lymphocytes ≤1100 cells/μL (OR, 1.67; 95% CI, 1.18 to 2.37; p =0.0033), LDH >320 U/I (OR, 1.69; 95% CI, 1.18 to 2.42; p =0.0039), AST >35 mg/dL (OR, 1.74; 95% CI, 1.2 to 2.52; p =0.003), sodium <135 mmol/L (OR, 2.32; 95% CI, 1.24 to 4.33; p =0.0079), and C-reactive protein >8 mg/dL (OR, 2.42; 95% CI, 1.72 to 3.41; p <0.0001). Conclusions Young patients with COVID-19 requiring hospital admission showed a notable incidence of respiratory failure. Obesity, SAHS, alcohol abuse, and certain laboratory parameters were independently associated with the development of this complication. Patients who suffered respiratory failure had a higher mortality and a higher incidence of major cardiac events, venous thrombosis, and hospital stay.