Potential risk factor | Study supports risk | Study does not support risk or is neutral |
---|---|---|

Sex |
Odds ratio for severe disease 3.68 for men compared to women (multivariable regression) [36] Odds ratio for invasive mechanical ventilation 2.83 for men compared to women (multivariable regression) [37] Females less likely to be admitted to ICU, require mechanical ventilation, or die; odds ratio 0.61 (multivariable logistic regression) [31] |
Sex distribution similar in severe and non-severe disease (descriptive) [30, 49] Sex distribution similar in severe and non-severe disease (statistical test) [23, 26, 28, 29, 32, 34, 38, 39, 41,42,43,44, 48,49,50] Sex distribution similar in severe and non-severe disease (multivariable regression) [19, 20] |

Age |
Average^{a} 61 years severe disease, 45 otherwise (statistical test) [38]Average ^{a} 61 years severe disease, 52 years moderate disease (statistical test) [23]Average ^{a} 56 years severe disease, 44 years mild disease (statistical test) [39]Median 67 years acute respiratory distress syndrome, 52 severe, 45 mild (statistical test) [42] Median 64 years severe patients, 52 years otherwise (statistical test) [48] Mean 61 years severe, otherwise 40 (statistical test) [50] Median 71 years SpO _{2} < 90%, 37 years SpO_{2} ≥ 90% (statistical test) [43]Median 66 years patients in ICU, 51 otherwise (statistical test) [41] Median 54 years patients in ICU, 41 otherwise (statistical test) [26] 65 years and over 3.26 times the hazard rate of ARDS than those under 65 (univariable regression) [44] Age associated with ICU admission, odds ratio 1.06 but unclear for what categorisation of age (multivariable regression) [20] |
Distribution of age did not differ by disease severity (descriptive) [30, 34, 49] Distribution of age did not differ by disease severity (statistical test) [28, 29, 32] Confidence interval for effect of age (categorisation unclear) crosses the null (multivariable regression) [37] |

Mean 56 years severe disease, 45 years mild disease; odds ratio 1.06 but unclear categorisation of age (multivariable regression) [36] Mean 63 years severe disease, 41 years mild disease; odds ratio 1.08 but unclear categorisation of age (multivariable regression) [19] Older individuals more likely to be admitted to ICU, require mechanical ventilation, or die; odds ratio 1.05, categories of age unclear (multivariable logistic regression) [31] | ||

Ethnicity | 76.3% of individuals receiving basic respiratory support were White versus 65.6% receiving advanced respiratory support; Asian and Black ethnicities appear most at risk of severe disease (England, Northern Ireland and Wales; descriptive) [30] | Distribution of disease severity similar across ethnic groups (Chinese, Malay, Indian, other – with small numbers in groups other than Chinese; study in Singapore; descriptive) [26] |

Deprivation | Distribution across deprivation categories similar (descriptive) [30] | |

Pregnancy | Distribution in pregnant and non-pregnant individuals similar across disease severity (descriptive) [30] | |

Smoking | 100% of current smokers had severe disease, but only six individuals smoked [50] |
Distribution in current and non-current smokers similar across disease severity (descriptive), only three individuals smoked [39] Distribution in current and non-current smokers similar across disease severity (statistical test); small numbers who smoked [29] Distribution in historical/current and non-smokers similar across disease severity (statistical test) [36, 48] |

Body mass index |
≥35 kg/m^{2} risk factor versus < 25 kg/m^{2} for invasive mechanical ventilation; odds ratio 7.36. Results for other strata cross the null (multivariable regression) [37]Increasing body mass index increased risk; odds ratio 1.17 (categorisation unclear) [19] | Distribution of disease severity similar across body mass index categories (descriptive) [30] |

Any/other comorbidity | Presence of comorbidity more common among those with severe disease (statistical test) [39, 41, 48, 50] |
Distribution with and without condition similar across disease severity (statistical test) [23, 29, 36] Distribution with and without comorbidities not otherwise considered in the study similar across disease severity (statistical test) [50] Distribution with and without condition similar across disease severity (multivariable regression) [20] |

Cardiovascular disease/chronic heart disease/coronary heart disease |
Presence of comorbidity more common among those with severe disease (descriptive) [39] Presence of comorbidity more common among those with severe disease (statistical test) [19, 36, 41, 43, 50] |
Distribution with and without condition similar across disease severity (descriptive) [30, 44] Distribution with and without condition similar across disease severity (statistical test) [29, 48] |

Hypertension |
Presence of comorbidity more common among those with severe disease (statistical test) [41, 43, 50] Hazard ratio of ARDS 1.82 in those with the condition versus those without (univariable regression) [44] Odds ratio of severe disease 2.71 in those with the condition versus those without (multivariable regression) [36] Odds ratio of being admitted to ICU, require mechanical ventilation, or die 1.89 in those with the condition versus those without (multivariable regression) [31] |
Distribution with and without condition similar across disease severity (descriptive) [39] Distribution with and without condition similar across disease severity (statistical test); one study with small numbers with the condition [23, 29, 42, 48] Confidence interval in presence and absence of condition crosses the null (multivariable regression) [19] Confidence interval in presence and absence of condition crosses the null (multivariable regression, result borderline) [37] |

Diabetes |
Presence of comorbidity more common among those with severe disease (descriptive) [39] Presence of comorbidity more common among those with severe disease (statistical test) [19, 36, 41, 43, 50] Hazard ratio of ARDS 2.34 in those with the condition versus those without (univariable regression) [44] Odds ratio of being admitted to ICU, require mechanical ventilation, or die 2.21 in those with the condition versus those without (multivariable regression) [31] |
Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [23] Distribution with and without condition similar across disease severity (statistical test) [29, 48] Distribution with and without condition similar across disease severity (statistical test, borderline result) [42] Confidence interval in presence and absence of condition crosses the null (multivariable regression) [37] |

Respiratory/pulmonary disease | Distribution with and without condition similar across disease severity (descriptive) [30, 39] | |

Asthma | Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [43] | |

Chronic obstructive pulmonary disease (COPD) |
Presence of comorbidity more common among those with severe disease (descriptive); small numbers with condition [39] Presence of comorbidity more common among those with severe disease (statistical test); both studies have small numbers with the condition [41, 50] Odds ratio of being admitted to ICU, require mechanical ventilation, or die 3.40 in those with the condition versus those without (multivariable regression) [31] | Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [29, 43, 48] |

Pulmonary tuberculosis | Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [48] | |

Malignancy |
Presence of comorbidity more common among those with severe disease (statistical test); small numbers with condition [39] Presence of comorbidity more common among those with severe disease (statistical test) [36, 42, 50] Presence of comorbidity more common among those with severe disease (multivariable analysis) [31] |
Distribution with and without condition similar across disease severity (descriptive) [30] Distribution with and without condition similar across disease severity (statistical test) [41] Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [19, 29, 43] |

Cerebrovascular disease | Presence of comorbidity more common among those with severe disease (statistical test) [41] | |

Arrhythmia | Distribution with and without condition similar across disease severity (statistical test); small numbers with the condition [48] | |

Cerebral infarction | Distribution with and without condition similar across disease severity (statistical test) [42] | |

Stroke | Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [48] | |

Aorta sclerosis | Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [48] | |

Chronic kidney disease/renal issues | Presence of comorbidity more common among those with severe disease (statistical test) [42] |
Distribution with and without condition similar across disease severity (descriptive) [30] Distribution with and without condition similar across disease severity (statistical test); small numbers with the condition [41] |

Chronic renal disease/insufficiency | Distribution with and without condition similar across disease severity (statistical test); one study has small numbers of patients with the condition [36, 48] | |

Chronic liver disease |
Distribution with and without condition similar across disease severity (descriptive), sometimes small numbers with condition [19, 30, 39] Distribution with and without condition similar across disease severity (statistical test) [36, 41] Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [29, 50] | |

Fatty liver and abnormal liver function | Distribution with and without condition similar across disease severity (statistical test) [48] | |

Hyperlipidaemia | Distribution with and without condition similar across disease severity (statistical test) [48] | |

Dyslipidemia | Confidence interval in presence and absence of condition crosses the null (multivariable regression) [37] | |

Chronic gastritis/gastric ulcer | Distribution with and without condition similar across disease severity (statistical test) [48] | |

Cholelithiasis | Distribution with and without condition similar across disease severity (statistical test) [48] | |

Urolithiasis | ||

Thyroid diseases | Distribution with and without condition similar across disease severity (statistical test); small numbers with the condition [48] | |

Electrolyte imbalance | Presence of comorbidity more common among those with severe disease (statistical test); small numbers with condition [48] | |

Agglomerative disease | Distribution with and without condition similar across disease severity (descriptive); small numbers with the condition [39] | |

Immunocompromised | Distribution with and without condition similar across disease severity (descriptive) [30] | |

Chronic hepatitis | Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [43] | |

HIV | Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [41] | |

Living without assistance | Distribution with and without condition similar across disease severity (descriptive) [30] |