Table 2. Characteristics of the included literature.
| Author | Research type | Group | Number of people | Age (years) | Complications |
|---|---|---|---|---|---|
| Qian GQ (10) | Multicenter retrospective study | Mild symptom | 82 | 49 | Not reported |
| Severe symptom | 9 | 66 | Not reported | ||
| Xie Y (11) | Single retrospective study | Mild symptom | 22 | 58 | Not reported |
| Severe symptom | 7 | 69 | Not reported | ||
| Zhu Z (12) | Single retrospective study | Mild symptom | 111 | 49.9±15 | High blood pressure 50%, heart disease 12.5%, cancer 6.25%, COPD 12.5% |
| Severe symptom | 16 | 57.5±11 | Diabetes 9.01%, hypertension 20.72%, heart disease 3.6%, cancer 3.6%, chronic obstructive pulmonary disease 3.6% | ||
| Zheng F (13) | Single retrospective study | Mild symptom | 131 | 40 | Diabetes 3.8%, hypertension 7.6%, heart disease 1.5%, chronic obstructive pulmonary disease 3.1%, cerebrovascular disease 2.3%, chronic liver disease 3.1% |
| Severe symptom | 30 | 57 | Diabetes 6.7%, hypertension 40%, heart disease 6.7%, chronic obstructive pulmonary disease 6.7%, cerebrovascular disease 3.3% | ||
| Lv Z (14) | Multicenter retrospective study | Mild symptom | 115 | 62 | Diabetes 7.83%, hypertension 20%, coronary heart disease 4.35%, chronic obstructive pulmonary disease 1.74% |
| Severe symptom | 155 | 61 | Diabetes 11.6%, hypertension 21.29%, heart disease 4.52%, chronic obstructive pulmonary disease 1.94% | ||
| Zhang G (15) | Single retrospective study | Mild symptom | 166 | 51 | Diabetes 9%, hypertension 16.9%, heart disease 5.4%, chronic obstructive pulmonary disease 1.2%, chronic kidney disease 0.6%, cerebrovascular disease 2.4%, chronic liver disease 1.8%, tumor 1.2%, |
| Severe symptom | 55 | 62 | Diabetes 12.7%, hypertension 47.3%, heart disease 23.6%, chronic obstructive pulmonary disease 7.3%, chronic kidney disease 9.1%, cerebrovascular disease 20%, chronic liver disease 7.3%, tumor 7.8%, immunosuppression 1.8% | ||
| Zhang H (16) | Multicenter retrospective study | Mild symptom | 9 | 47±11.7 | Not reported |
| Severe symptom | 4 | 55.2±6 | Not reported | ||
| Fu J (17) | Single retrospective study | Mild symptom | 22 | 40.7±9 | Hyperlipidemia 4.5% |
| Severe symptom | 13 | 60±15.5 | Diabetes 23.1%, hypertension 38.5%, chronic obstructive pulmonary disease 7.7%, cerebrovascular | ||
| Liu SL (18) | Single retrospective study | Mild symptom | 194 | 43 | Not reported |
| Severe symptom | 31 | 64 | Not reported | ||
| Liu Q (19) | Multicenter retrospective study | Mild symptom | 59 | 49 | Diabetes 3.4%, chronic kidney disease 4%, cerebrovascular disease 1.7%, chronic obstructive pulmonary disease 3.4% |
| Mild symptom | 25 | 52 | Diabetes 12%, chronic kidney disease 4%, heart disease 8%, cancer 4%, COPD 12% | ||
| Xu B (20) | Single retrospective study | Mild symptom | 80 | 56 | Not reported |
| Severe symptom | 45 | 60 | Not reported | ||
| Burgos-Blasco B (21) | Single retrospective study | Mild symptom | 35 | 68.5 | Cardiovascular disease 31%, chronic kidney disease 6%, chronic liver disease 6%, tumor 6% |
| Severe symptom | 27 | 71 | Cardiovascular disease 41%, chronic kidney disease 19%, chronic liver disease 4%, tumor 15% | ||
| Vultaggio A (22) | Single retrospective study | Mild symptom | 63 | 72±13 | Cardiovascular disease 41%, chronic kidney disease 19%, chronic liver disease 4%, tumor 15% |
| Severe symptom | 145 | 63±15 | Diabetes 27%, hypertension 58.7%, chronic lung disease 17.5%, cardiovascular disease 11.1% | ||
| Gao Y (23) | Single retrospective study | Mild symptom | 28 | 42.96±14 | Diabetes 3.57%, hypertension 25%, heart disease 8% |
| Severe symptom | 15 | 45±7.68 | Diabetes 40%, hypertension 40%, heart disease 6% | ||
| Zeng Z (24) | Single retrospective study | Mild symptom | 93 | 59 | Diabetes 18.3%, hypertension 43%, chronic kidney disease 3.2%, tumor 3.2%, chronic respiratory disease 4.3%, heart disease 10.8% |
| Severe symptom | 167 | 62 | Diabetes 18%, hypertension 36.5%, chronic kidney disease 0.6%, tumor 1.2%, chronic respiratory disease 5.9%, heart disease 10.8%, 8.4% | ||
| Liu J (25) | Single retrospective study | Mild symptom | 13 | 59.7±10.1 | Diabetes 30.8%, hypertension 38.5%, pituitary adenoma 7.7% |
| Severe symptom | 27 | 43.2±12.3 | Diabetes 7.4%, hypertension 3.7%, pituitary adenoma 3.7% |
COPD, chronic obstructive pulmonary disease.