Table 1.
Characteristics of included studies (N = 116).
| Variables | N (%) | |
|---|---|---|
| Mean age | <60 years | 86 (74) |
| ≥60 years | 27 (23) | |
| Unclear | 3 (3) | |
| Male proportion | <50% | 77 (66) |
| ≥50% | 34 (29) | |
| Unclear | 5 (4) | |
| Location | Asia | 56 (48) |
| Europe | 25 (22) | |
| America | 18 (16) | |
| Oceania | 5 (4) | |
| Africa | 3 (3) | |
| Unclear | 9 (8) | |
| Latitude | <30o | 14 (12) |
| 30o- 59o | 89 (77) | |
| ≥60o | 6 (5) | |
| Unclear | 7 (6) | |
| Co-supplementation with Calcium | Yes | 6 (5) |
| No | 110 (95) | |
| Detection method of 25(OH)D | LC–MS | 22 (19) |
| ELISA | 36 (31) | |
| Chemiluminescence | 23 (20) | |
| Radioimmunoassay | 9 (8) | |
| Others | 15 (13) | |
| Unclear | 11 (10) | |
| Participants having any disease at baseline | No | 29 (25) |
| Yes | 80 (69) | |
| Unclear | 7 (6) | |
| Baseline vitamin D deficiency | No | 86 (74) |
| Yes | 30 (26) |
LC–MS indicates liquid chromatography-mass spectrometry; ELISA indicates enzyme-linked immunosorbent assay.