Bonifazi 2021.

Study characteristics
Notes	English title Predictors of worse prognosis in young and middle‐aged adults hospitalized with COVID‐19 pneumonia: a multi‐center Italian study (COVID‐UNDER50) Study setting Start of study recruitment (MM/YYYY) 02/2020 End of study recruitment (MM/YYYY) 05/2020 Study design retrospective cohort Study centre(s) multiple centres/clinics/areas within a country Number of centres/clinics/areas 9 Study setting inpatient Number of participants recruited 263 Sampling method consecutive participants Participants Female participants (absolute number), 99 Age measure, value median (Interquartile range), 45.3 (40.4, 48.4) Inclusion criteria patients, aged 18–50 years, hospitalised for confirmed or probable diagnosis of SARS‐CoV2 infection Exclusion criteria NR Smoking NR Diabetes NR Hypertension NR Cardiovascular diseases NR Please indicate if additional information is available  NR Asthma NR Chronic obstructive pulmonary disease NR Other pulmonary diseases NR Please indicate if additional information is available  NR Immunosuppression NR Please indicate if additional information is available NR Chronic kidney disease NR Cancer NR Steroid administration NR Supplemental oxygen (absolute number), 88 Differential values for various oxygenation methods (if indicated) NR Other treatment NR Dose if applicable NR Duration if applicable NR Percentage received this treatment NR Prognostic factor(s) Study’s definition for obesity up to normal weight (BMI < 25 kg/m2), overweight (25 ≤ BMI < 30 kg/m2) and obese (BMI ≥ 30 kg/m2). The time when obesity has been measured before disease or right at presentation Main variable used for determination of obesity BMI Threshold used for definition of obesity  BMI ≥ 30 kg/m2 Measure of frequency absolute number Frequency value 51 How many eligible outcomes reported? 2 How many eligible outcomes reported? 2 Outcome(s) Mechanical ventilation, mortality Outcome (prognostic factor) Mechanical ventilation (BMI ≥ 30 kg/m2) Outcome Mechanical ventilation Prognostic factor (category):  BMI ≥ 30 kg/m2 Follow‐up Number of patients followed completely for this outcome  263 Number of obese patients followed completely for this outcome  51 Number of non‐obese patients followed completely for this outcome  146 Univariable (unadjusted) analysis for obesity Effect measure for obesity NR Effect measure value (95% CI) NR Multivariable (adjusted) analysis for obesity Modelling method logistic regression The set of prognostic factors used for adjustment Age, comorbidities, smoking status, sex Effect measure for obesity odds ratio  Effect measure value (95% CI) 3.5 (1.44, 8.79) Outcome (prognostic factor) Mechanical ventilation (25 < BMI < 30 (overweight)) Outcome Mechanical ventilation Prognostic factor (category):  25 < BMI < 30 (overweight) Follow‐up Number of patients followed completely for this outcome  263 Number of obese patients followed completely for this outcome  51 Number of non‐obese patients followed completely for this outcome  146 Univariable (unadjusted) analysis for obesity Effect measure for obesity NR Effect measure value (95% CI) NR Multivariable (adjusted) analysis for obesity Modelling method logistic regression The set of prognostic factors used for adjustment Age, comorbidities, smoking status, sex Effect measure for obesity odds ratio  Effect measure value (95% CI) 1.43 (0.54, 3.81) Outcome (prognostic factor) mortality (BMI ≥ 30 kg/m2) Outcome mortality Prognostic factor (category):  BMI ≥ 30 kg/m2 Follow‐up Number of patients followed completely for this outcome  263 Number of obese patients followed completely for this outcome  51 Number of non‐obese patients followed completely for this outcome  146 Univariable (unadjusted) analysis for obesity Effect measure for obesity NR Effect measure value (95% CI) NR Multivariable (adjusted) analysis for obesity Modelling method Cox regression The set of prognostic factors used for adjustment Age, comorbidities Effect measure for obesity odds ratio  Effect measure value (95% CI) 0.79 (0.27, 2.27) Outcome (prognostic factor) mortality (25 < BMI < 30 (overweight)) Outcome mortality Prognostic factor (category):  25 < BMI < 30 (overweight) Follow‐up Number of patients followed completely for this outcome  263 Number of obese patients followed completely for this outcome  51 Number of non‐obese patients followed completely for this outcome  146 Univariable (unadjusted) analysis for obesity Effect measure for obesity NR Effect measure value (95% CI) NR Multivariable (adjusted) analysis for obesity Modelling method Cox regression The set of prognostic factors used for adjustment Age, comorbidities Effect measure for obesity odds ratio  Effect measure value (95% CI) 0.29 (0.05, 1.74)
Item	Authors' judgement	Support for judgement
Study Participation	Unclear	Appendix 3
Study Attrition Mortality	Yes	Appendix 3
Study Attrition Mechanical ventilation	Yes	Appendix 3
Prognostic Factor Measurement	Unclear	Appendix 3
Outcome Measurement Mortality	Yes	Appendix 3
Outcome Measurement Mechanical ventilation	Yes	Appendix 3
Confounding Bias Mortality	Unclear	Appendix 3
Confounding Bias Mechanical ventilation	Unclear	Appendix 3
Statistical Analysis Bias	Yes	Appendix 3