Gao 2021.

Study characteristics
Notes	English title Associations between body‐mass index and COVID‐19 severity in 6·9 million people in England: a prospective, community‐based, cohort study Study setting Start of study recruitment (MM/YYYY) 01/2020 End of study recruitment (MM/YYYY) 04/2020 Study design prospective cohort Study centre(s) multiple centres/clinics/areas within a country Number of centres/clinics/areas NR Study setting outpatient Number of participants recruited 6,910,695 Sampling method unspecified Participants Female participants (percentage), 53.1 Age measure, value (reported in categories) 20 to 39 years: 2,384,223 (34.5%) 40 to 59 years: 2,444,011 (35.4%) 60 to 79 years: 1,652,615 (23.9%) >= 80 years: 429,846 (6.2%) Inclusion criteria aged 20–99 years who were registered at a general practice (GP) that contributes to the QResearch database and had available BMI data. Exclusion criteria Participants without at least one BMI measurement Smoking (percentage), 17.1 Diabetes (percentage), 8.4 Hypertension (percentage), 19.7 Cardiovascular diseases (percentage), 6 Please indicate if additional information is available  NR Asthma (unspecified) Chronic obstructive pulmonary disease (unspecified) Other pulmonary diseases (percentage), 16.1 Please indicate if additional information is available  COPD and asthma Immunosuppression (unspecified) Please indicate if additional information is available NR Chronic kidney disease (percentage), 4.7 Cancer (unspecified) Steroid administration (unspecified) Supplemental oxygen (unspecified) 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 Obesity l: BMI = 30‐34.9, obesity ll/lll = +35 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 Measure of frequency absolute number Frequency value 1,681,112 How many eligible outcomes reported? 3 How many eligible outcomes reported? 3 Outcome(s) hospitalisation, ICU admission, mortality Outcome (prognostic factor) hospitalisation (BMI) Outcome hospitalisation Prognostic factor (category):  BMI Follow‐up Number of patients followed completely for this outcome  6,910,695 Number of obese patients followed completely for this outcome  1,681,112 Number of non‐obese patients followed completely for this outcome  5,229,583 Univariable (unadjusted) analysis for obesity Effect measure for obesity hazard ratio Effect measure value (95% CI) 1.05 (1.05, 1.06) Multivariable (adjusted) analysis for obesity Modelling method Cox regression The set of prognostic factors used for adjustment Age, sex, ethnicity, economic status, geographical region, smoking status, non‐obesity‐related morbidity, including conditions related to severe COVID‐19 disease (namely, chronic obstructive pulmonary disease, asthma, autoimmune diseases [systemic lupus erythematosus, rheumatoid diseases], ulcerative colitis or Crohn’s disease, type 1 diabetes, chronic liver disease, chronic renal disease, chronic neurological disease, and cerebral palsy); obesity‐related morbidity, including hypertension, cardiovascular disease (including congestive heart failure and stroke), reflux disease or gastro‐oesophageal reflux disease, and sleep apnoea; and type 2 diabetes Effect measure for obesity hazard ratio Effect measure value (95% CI) 1.04 (1.04, 1.05) Outcome (prognostic factor) ICU admission (BMI) Outcome ICU admission Prognostic factor (category):  BMI Follow‐up Number of  patients followed completely for this outcome  6,910,695 Number of obese patients followed completely for this outcome  1,681,112 Number of non‐obese patients followed completely for this outcome  5,229,583 Univariable (unadjusted) analysis for obesity Effect measure for obesity hazard ratio Effect measure value (95% CI) 1.1 (1.09, 1.11) Multivariable (adjusted) analysis for obesity Modelling method Cox regression The set of prognostic factors used for adjustment Age, sex, ethnicity, economic status, geographical region, smoking status, non‐obesity‐related morbidity, including conditions related to severe COVID‐19 disease (namely, chronic obstructive pulmonary disease, asthma, autoimmune diseases [systemic lupus erythematosus, rheumatoid diseases], ulcerative colitis or Crohn’s disease, type 1 diabetes, chronic liver disease, chronic renal disease, chronic neurological disease, and cerebral palsy); obesity‐related morbidity, including hypertension, cardiovascular disease (including congestive heart failure and stroke), reflux disease or gastro‐oesophageal reflux disease, and sleep apnoea; and type 2 diabetes Effect measure for obesity hazard ratio Effect measure value (95% CI) 1.09 (1.08, 1.1) Outcome (prognostic factor) mortality (BMI) Outcome mortality Prognostic factor (category):  BMI Follow‐up Number of patients followed completely for this outcome  6,910,695 Number of obese patients followed completely for this outcome  1,681,112 Number of non‐obese patients followed completely for this outcome  5,229,583 Univariable (unadjusted) analysis for obesity Effect measure for obesity hazard ratio Effect measure value (95% CI) 1.03 (1.03, 1.02) Multivariable (adjusted) analysis for obesity Modelling method Cox regression The set of prognostic factors used for adjustment Age, sex, ethnicity, economic status, geographical region, smoking status, non‐obesity‐related morbidity, including conditions related to severe COVID‐19 disease (namely, chronic obstructive pulmonary disease, asthma, autoimmune diseases [systemic lupus erythematosus, rheumatoid diseases], ulcerative colitis or Crohn’s disease, type 1 diabetes, chronic liver disease, chronic renal disease, chronic neurological disease, and cerebral palsy); obesity‐related morbidity, including hypertension, cardiovascular disease (including congestive heart failure and stroke), reflux disease or gastro‐oesophageal reflux disease, and sleep apnoea; and type 2 diabetes Effect measure for obesity hazard ratio Effect measure value (95% CI) 1.04 (1.04, 1.05)
Item	Authors' judgement	Support for judgement
Study Participation	Unclear	Appendix 3
Study Attrition Mortality	Yes	Appendix 3
Study Attrition ICU admission	Yes	Appendix 3
Study Attrition Hospitalisation	Yes	Appendix 3
Prognostic Factor Measurement	Yes	Appendix 3
Outcome Measurement Mortality	Yes	Appendix 3
Outcome Measurement ICU admission	Yes	Appendix 3
Outcome Measurement Hospitalisation	Yes	Appendix 3
Confounding Bias Mortality	Yes	Appendix 3
Confounding Bias ICU admission	Yes	Appendix 3
Confounding Bias Hospitalisation	Yes	Appendix 3
Statistical Analysis Bias	Yes	Appendix 3