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Table 5 Potential risk factors for disease severity

From: Informing the public health response to COVID-19: a systematic review of risk factors for disease, severity, and mortality

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 Averagea 61 years severe disease, 45 otherwise (statistical test) [38]
Averagea 61 years severe disease, 52 years moderate disease (statistical test) [23]
Averagea 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 SpO2 < 90%, 37 years SpO2 ≥ 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/m2 risk factor versus < 25 kg/m2 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   Distribution with and without condition similar across disease severity (statistical test); small numbers with condition [48]
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]
  1. One study included death in a combined measure of disease severity [31]. aUnclear as to whether mean, median or mode. ARDS acute respiratory distress syndrome, ICU intensive care unit, SpO2 oxygen saturation