Table 1. The meta-analysis of risk factors for severe patients with COVID-19.

Risk factor	Definition	Number of studies	Size (n)	OR/WMD/SMD (CI 95%)	I2
Patient characteristics
Age (year)	Continuous	6	681	11.89 [8.63, 15.14]	54.40%
Gender	Male vs. Female	10	1494	1.61 [1.25, 2.07]	0%
BMI (kg/m2)	Continuous	2	79	3.38 [0.07, 6.69]	67.20%
Smoking	Yes vs. No	3	412	1.4 [0.65, 3.01]	0%
Comorbidities
Diabetes	Yes vs. No	10	1083	3.04 [2.01, 4.60]	20.40%
Hypertension	Yes vs. No	10	1083	2.31 [1.68, 3.18]	47.10%
Cardiovascular disease	Yes vs. No	7	906	2.76 [1.39, 5.45]	25.70%
Chronic obstructive pulmonary disease	Yes vs. No	5	623	3.56 [1.33, 9.54]	0%
Vital Signs
Respiratory rate (per min)	Continuous	2	70	5.29 [2.56, 8.01]	42.80%
Symptoms
Fever	Yes vs. No	10	2032	2.11 [1.11, 4.02]	64.20%
Dyspnea	Yes vs. No	8	977	8.83 [2.82, 27.67]	79.10%
Laboratory Findings
Blood routine
White blood cell count (×10^9/L)	Continuous	7	595	1.76 [0.31, 3.22]	88.70%
Lymphocytes count (×10^9/L)	Continuous	6	563	-0.42 [-0.52, -0.33]	11.50%
Neutrophils count (×10^9/L)	Continuous	2	159	2.92 [-1.33, 7.17]	93%
Biochemical indicators
Albumin (g/L)	Continuous	4	323	-5.74 [-7.94, -3.54]	62.80%
Alanine aminotransferase (IU/L)	Continuous	4	189	16.97 [2.18, 31.76]	89.10%
Aspartate aminotransferase (IU/L)	Continuous	4	229	20.60 [6.81, 34.40]	86.90%
Lactate dehydrogenase (umol/L)	Continuous	3	120	3.93 [2.01, 5.86]	0%
Creatinine (umol/L)	Continuous	5	422	8.32 [-1.63, 18.28]	62.10%
Inflammatory biomarkers
C-reactive protein (SMD)	Continuous	5	463	2.11 [0.71, 3.51]	96.10%
Procalcitonin (ng/ml)	Continuous	5	455	0.16 [0.04, 0.28]	77.80%
Myocardial enzymes
Lactate dehydrogenase (SMD)	Continuous	5	291	2.0 [1.20, 2.80]	81.10%
Creatine kinase (IU/L)	Continuous	3	213	23.55 [17.08, 30.02]	30.80%
Coagulation
D-dimer (mg/L)	Continuous	5	396	0.67 [0.02, 1.32]	72%