Table 1. Quality assessment and baseline characteristics of the included studies.
| Study and year | Quality assessment | Country | Publishing language | Sample size | Males/Females | Age | Cerebrovascular disease, (%) | Hypertension, (%) | Dizziness or headache, (%) |
| Li,2020[8] | ★★★★★★ | China | Chinese | 80 | 40/40 | 3-90 | — | 14, (17.5) | 12, (15.0) |
| Yuan,2020[9] | ★★★★★ | China | Chinese | 223 | 106/117 | 46.5±16.1 | — | 25, (11.2) | 11, (4.9) |
| Wang,2020a[10] | ★★★★ | China | Chinese | 32 | 16/16 | — | — | 5, (15.6) | 1, (3.1) |
| Zhang,2020a[11] | ★★★★ | China | Chinese | 61 | 36/25 | 3-85 | — | 15, (24.6) | 9, (14.8) |
| Zuo,2020[12] | ★★★★★ | China | Chinese | 50 | 18/32 | 48.2±15.3 | 2, (4.0) | 9, (18.0) | 3, (6.0) |
| Wang,2020b[13] | ★★★★ | China | Chinese | 96 | 46/50 | — | 3, (3.1) | 50, (52.1) | 2, (2.1) |
| Lei,2020[14] | ★★★★ | China | Chinese | 51 | 25/16 | 26-82 | 1, (1.96) | 9, (17.6) | 1, (1.96) |
| Dong,2020[15] | ★★★★★★ | China | Chinese | 27 | 13/14 | 23-68 | — | 4, (14.8) | 4, (14.8) |
| Zhao,2020[16] | ★★★★ | China | Chinese | 21 | 14/7 | 4-72 | — | 4, (19.0) | 4, (19.0) |
| Tong,2020[17] | ★★★ | China | Chinese | 258 | 133/125 | 46.97±17.8 | 1, (0.39) | 32, (12.4) | — |
| Suo,2020[18] | ★★★★★ | China | Chinese | 171 | 67/104 | 49±20 | — | 24, (14) | 16, (9.4) |
| Zhong,2020[19] | ★★★★ | China | Chinese | 62 | 40/22 | 28-77 | — | — | 2, (3.2) |
| Xu,2020a[20] | ★★★★★ | China | Chinese | 155 | 87/68 | 41.99±15.40 | — | — | 5, (3.2) |
| Gong,2020[21] | ★★★★★★ | China | Chinese | 80 | 45/35 | 18-82 | — | 8, (10.0) | 10, (8.0) |
| Chen,2020a[22] | ★★★★★ | China | Chinese | 67 | 20/47 | 11-85 | — | 12, (17.9) | — |
| Lu,2020[23] | ★★★★★ | China | Chinese | 50 | 28/22 | 50.4±16.8 | — | 8, (16) | — |
| Huang,2020a[24] | ★★★★ | China | Chinese | 35 | 19/16 | 12-74 | — | 1, (2.9) | 3, (8.6) |
| Liang,2020a[25] | ★★★ | China | Chinese | 28 | 16/12 | 24-87 | 1, (3.6) | 9, (32.1) | — |
| Zhuang,2020[26] | ★★★★ | China | Chinese | 26 | 18/8 | 3-79 | — | 4, (15.4) | 6, (23.1) |
| Yang,2020[27] | ★★★★★★ | China | English | 149 | 81/68 | 45.11±13.35 | 0, (0) | — | 13, (8.7) |
| Chen,2020b[28] | ★★★★★★ | China | English | 249 | 126/123 | 51±20.74 | — | — | 28, (11.2) |
| Liu,2020a[29] | ★★★★★ | China | English | 56 | 31/25 | — | — | 10, (17.9) | — |
| Lovell,2020[30] | ★★★★★★★ | British | English | 101 | 64/37 | 82.0±12.6 | 12, (11.9) | 54, (53.5) | — |
| Huang,2020b[31] | ★★★★★★★ | China | English | 41 | 30/11 | 49.0±12.6 | — | 6, (14.6) | 3, (7.9) |
| Chen,2020c[32] | ★★★★★★★ | China | English | 99 | 67/32 | 55.5±13.1 | 1, (1.0) | — | 8, (8.1) |
| Zhou,2020a[33] | ★★★★★★★★ | China | English | 191 | 119/72 | 56.0±15.6 | — | 58, (30.3) | — |
| Goyal,2020[34] | ★★★★ | America | English | 393 | 238/155 | 62.2±18.6 | — | 197, (50.1) | — |
| Guan,2020[35] | ★★★★★★★★ | China | English | 1099 | 640/459 | 47.0±17.0 | 15, (1.4) | 165, (15.0) | 150, (13.6) |
| Chen,2020d[36] | ★★★★★★ | China | English | 203 | 108/95 | 20-91 | 43, (21.2) | 9, (4.4) | 14, (6.9) |
| Qian,2020[37] | ★★★★ | China | English | 91 | 37/54 | 5-96 | — | 15, (16.5) | 7, (7.7) |
| Liu,2020b[38] | ★★★★★★★ | China | English | 137 | 61/76 | 20-83 | — | 13, (9.5) | 13, (9.5) |
| Zhang,2020b[39] | ★★★★★ | China | English | 140 | 71/69 | 25-87 | 3, (2.1) | 42, (30) | — |
| Zhou,2020b[40] | ★★★★★★ | China | English | 21 | 13/8 | 66.1±13.9 | 3, (14.3) | 10, (47.6) | 0, (0) |
| Xu,2020b[41] | ★★★★★★★ | China | English | 62 | 35/27 | 41.0±15.6 | 1, (1.6) | 5, (8.1) | 21, (33.9) |
| Chen,2020e[42] | ★★★★★★ | China | English | 274 | 171/103 | 62.0±19.3 | 4, (1.5) | 93, (33.9) | 52, (19.0) |
| Zheng,2020a[43] | ★★★★★ | China | English | 96 | 58/38 | 55.0±15.2 | — | 35,(36.5) | 11, (11.5) |
| Liang,2020b[44] | ★★★★★★★ | China | English | 1590 | 904/674 | 48.9±16.3 | 30, (1.9) | 269, (16.9) | 205, (15.4) |
| Wang,2020c[45] | ★★★★★★★ | China | English | 138 | 75/63 | 56.0±19.3 | 7, (5.1) | 43, (31.2) | 21, (15.2) |
| Zheng,2020b[46] | ★★★ | China | English | 161 | 80/81 | 45±17.4 | 4, (2.5) | 22, (13.7) | 12, (7.5) |
| Wu,2020[47] | ★★★★★★ | China | English | 80 | 39/41 | 46.1±15.4 | 1, (1.3) | — | 13, (16.3) |
| Wang,2020d[48] | ★★★★ | China | English | 26 | 11/15 | 42.0±14.7 | — | 5, (19.2) | 1, (3.9) |
| Grasselli,2020[49] | ★★★★★★★★ | Italy | English | 1591 | 1304/287 | 63.0±10.4 | — | 509, (48.8) | — |
| Richardson,2020[50] | ★★★★★★★★ | America | English | 5700 | 3437/2263 | 0-107 | — | 3026, (53.1) | — |
| Wan,2020[51] | ★★★★★ | China | English | 135 | 72/63 | 47±14.1 | — | 13, (9.6) | 34, (25.2) |
| Xu,2020c[52] | ★★★★ | China | English | 90 | 39/51 | 18-86 | — | 17, (18.9) | 4, (4.4) |
| Wang,2020e[53] | ★★★★★ | China | English | 1012 | 524/488 | 16-89 | — | 46, (45.4) | 152, (15) |
| Zhang,2020c[54] | ★★★★ | China | English | 645 | 328/326 | 46.65±13.82 | — | 100, (15.5) | 67, (10.4) |