Table 1.
The basic characteristics of the studies included in the systematic review and meta-analyses
| Study | Location | Region | Study design | Sample size | Gender (men), n (%) | Population age mean±SD or median [Min-Max or IQR] | The definition of VDD and/or VDIS | Outcomes evaluated in the study | Included in the meta-analysis |
|---|---|---|---|---|---|---|---|---|---|
| Abdollahi et al. [27] | Iran | Asia | Case-control | 402 | 132 (32.8) | 47.1±15.3 | VDD<10 ng/mL | I | Yes |
| VDIS<30 ng/mL | |||||||||
| Baktash et al. [28] | UK | Europe | Cross-sectional | 105 | 57 (54.2) | 81 [65-102] | VDD<30 nmol/L | I-M | Yes |
| Campi et al. [29] | Italy | Europe | Cohort | 361 | 243 (67.0) | 66 [54–78] | VDD<50 nmol/L | I-S-M | Yes |
| Cereda et al. [30] | Italy | Europe | Cohort | 129 | 70 (54.3) | 77 [65–85] | VDD<20 ng/mL | S-M | Yes |
| VDIS<30 ng/mL | |||||||||
| D’Avolio et al. [21] | Switzerland | Europe | Case-control | 1,484 | 682 (45.9) | NR | NR | I | No |
| Darling et al. [22] | UK | Europe | Case-control | 1,303 | 713 (54.7) | 57.7±8.7 | NR | I | No |
| De Smet et al. [31] | Belgium | Europe | Cross-sectional | 2,903 | 1,108 (38.1) | NR | VDD<20 ng/mL | I-S | Yes |
| Hastie et al. [23] | UK | Europe | Cohort | 341,484 | NR | NR | VDD<25 nmol/L | I-M | No |
| VDIS<50 nmol/L | |||||||||
| Hernández et al. [32] | Spain | Europe | Case-control | 413 | 253 (61.2) | NR | VDD<20 ng/mL | I-S-M | Yes |
| Im et al. [24] | Korea | Asia | Case-control | 200 | 84 (42.0) | 52.3±20.3 | VDD<20 ng/dL | I-S | No |
| Israel et al. [33] | Israel | Asia | Case-control | 576,455 | 271,601 (47.1) | NR | VDD<50 nmol/L | I | Yes |
| Karahan and KatKat [34] | Turkey | Europe | Cross-sectional | 149 | 81 (54.3) | 63.5±15.3 | VDD<20 ng/mL | S-M | Yes |
| VDIS<30 ng/mL | |||||||||
| Katz et al. [25] | USA | America | Case-control | 987,849 | 455,458 (46.1) | NR | NR | I | No |
| Li et al. [35] | UK | Europe | Case-control | 353,299 | 161,298 (45.6) | 67.7±8.1 | VDD<25 nmol/L | I-H-S | Yes |
| VDIS<50 nmol/L | |||||||||
| Livingston et al. [36] | UK | Europe | Cohort | 104 | 39 (37.5) | 68.5±18.3 | VDSL<34.4 nmol/L | I | Yes |
| Luo et al. [37] | China | Asia | Cross-sectional | 895 | 405 (45.2) | NR | VDD<30 nmol/L | I-S-M | Yes |
| Macaya et al. [38] | Spain | Europe | Cohort | 80 | 35 (43.7) | NR | VDD<20 ng/mL | S | Yes |
| Maghbooli et al. [39] | Iran | Asia | Cross-sectional | 235 | 144 (61.3) | 58.7±15.2 | VDD<20 ng/mL | H-S-M | Yes |
| VDIS<30 ng/mL | |||||||||
| Mardani et al. [40] | Iran | Asia | Cross-sectional | 123 | 65 (52.8) | 42.1±14,9 | VDD<10 ng/mL | I | Yes |
| VDIS<30 ng/mL | |||||||||
| Meltzer et al. [41] | USA | America | Case-control | 489 | 123 (25.0) | 49.2±18.4 | VDD<20 ng/mL | I | Yes |
| Mendy et al. [42] | USA | America | Cohort | 689 | 365 (53.0) | 49.5 [35.2–67.5] | NR | H-S | Yes |
| Merzon et al. [43] | Israel | Asia | Case-control | 7,807 | 3,234 (41.4) | 41.4±NR | VDD<20 ng/mL | I-H | Yes |
| VDIS<30 ng/mL | |||||||||
| Panagiotou et al. [44] | UK | Europe | Cohort | 134 | 73 (54.4) | 68.7±14.0 | VDD<25 nmol/L | S | Yes |
| VDIS<50 nmol/L | |||||||||
| Radujkovic et al. [45] | Germany | Europe | Cohort | 185 | 95 (51.0) | 60 [49–70] | VDD<12 ng/mL | S-M | Yes |
| VDIS<20 ng/mL | |||||||||
| Vasiliou et al. [46] | Greece | Europe | Cohort | 39 | 31 (79.4) | 61.5±13.2 | VDD<20 ng/mL | H-M | Yes |
| VDIS<30 ng/mL | |||||||||
| Ye et al. [47] | China | Asia | Case-control | 142 | 55 (38.7) | NR [0.1-85] | VDD<50 nmol/L | I-S | Yes |
| VDIS<75 nmol/L |
SD, standard deviation; Min, minimun; Max, maximun; IQR, interquartile range; NR, not reported; VDD, vitamin D deficiency; VDIS, vitamin D insufficiency; VDSL, vitamin D serum level; H, hospitalization; I, COVID-19 infection; S, severity; M, mortality.