Table 1.
Characteristics of included studies.
| First author (year; location) | Study design | Sample | Population and sample size | Matching | Mean age (years) | Mean BMI | Method of assessment | Magnesium concentration, mmol/L (mean ± SD) | NOS | |
|---|---|---|---|---|---|---|---|---|---|---|
| Zhou (1) (2019; China) | CC | Serum | Prediabetes (IGF)/healthy | Cases: 12 | NR | NR | NR | Inductively coupled plasma spectrometer |
Cases: 0.88 ± 0.28 Controls: 1.45 ± 0.27 |
7 |
| Controls: 50 | ||||||||||
| Zhou (2) (2019; China) | CC | Serum | Prediabetes (IGT)/healthy | Cases: 15 | NR | NR | NR | Inductively coupled plasma spectrometer |
Cases: 0.94 ± 0.21 Controls: 1.45 ± 0.27 |
7 |
| Controls: 50 | ||||||||||
| Rahim (2018; Bangladesh) | CC | Serum | Prediabetes/healthy | Cases: 50 | Age, Sex |
Case: 43.68 Control: 43.26 |
Case: 27.70 Control: 25.33 |
NR |
Cases: 0.70 ± 0.14 Controls: 0.85 ± 0.15 |
9 |
| Controls: 50 | ||||||||||
| Chen (2017; China) | CC | Plasma | Prediabetes/healthy | Prediabetes: 867 | Age, Sex |
Case: 52.96 Control: 52.21 |
Case: 25.09 Control: 23.30 | Inductively coupled plasma mass spectrometry |
Cases: 0.88 ± 0.12 Controls: 0.91 ± 0.11 |
8 |
| Healthy: 2105 | ||||||||||
| Fang (2016; Chin) | NC | Serum | Prediabetes/healthy | Prediabetes: 145 | Gender, Age |
Case: 60.23 Control: 60.19 |
Case: 24.05 Control: 23.23 |
Flame atomic absorption spectroscopy |
Prediabetes: 0.90 ± 3.13 Healthy: 0.97 ± 3.73 |
9 |
| Healthy: 145 | ||||||||||
| Spiga (2019; Italy) | CS | Serum | Prediabetes/healthy | Prediabetes: 224 | NR |
Prediabetes: 51 Healthy: 44 |
Prediabetes: 31.5 Healthy: 30.1 |
Colorimetric method assay |
Prediabetes: 0.81 ± 0.07 Healthy: 0.82 ± 0.06 |
5 |
| Healthy: 365 | ||||||||||
| Aksit (2019; Turkey) | CS | Serum | Prediabetes/healthy | Prediabetes: 85 | NR |
Prediabetes: 34.5 Healthy: 29.75 |
NR | Photometric method |
Prediabetes: 0.84 ± 0.03 Healthy: 0.86 ± 0.05 |
5 |
| Healthy: 137 | ||||||||||
| Kieboom (2017; Netherlands) | CS | Serum | Prediabetes/healthy | Prediabetes: 1346 | NR |
Prediabetes: 66.6 Healthy: 64.3 |
Prediabetes: 28.5 Healthy: 26.7 |
Colorimetric endpoint method and the Roche/Hitachi Cobas c501 Analyzer |
Prediabetes: 0.84 ± 0.06 Healthy: 0.85 ± 0.06 |
6 |
| Healthy: 7209 | ||||||||||
| Yadav (2017; india) | CS | Serum | Prediabetes/healthy | Prediabetes: 35 | Age |
Prediabetes: 36.8 Healthy: 34.8 |
Prediabetes: 25.35 Healthy: 22.52 |
Semi-automated analyser |
Prediabetes: 0.56 ± 0.15 Healthy: 0.87 ± 0.09 |
7 |
| Healthy: 35 | ||||||||||
| Chambers (1) (2006; USA) | CS | Serum | Prediabetes (African American)/ healthy | Prediabetes: 78 | NR | NR | NR | NR |
Prediabetes: 0.85 ± 0.08 Healthy: 0.85 ± 0.08 |
5 |
| Healthy: 109 | ||||||||||
| Chambers (2) (2006; USA) | CS | Serum | Prediabetes (Hispanic)/healthy | Prediabetes: 70 | NR | NR | NR | NR |
Prediabetes: 0.83 ± 0.08 Healthy: 0.83 ± 0.09 |
5 |
| Healthy: 169 | ||||||||||
| Lind (1990; Sweden) | CS | Serum | Prediabetes/healthy | Prediabetes: 52 | Age, Sex | NR | NR | Atomic absorption |
Prediabetes: 0.79 ± 0.06 Healthy: 0.85 ± 0.06 |
6 |
| Healthy: 52 | ||||||||||
BMI Body Mass Index, CC Case–Control, CS cross sectional, NC Nested case–control, Mg Magnesium, ADA American Diabetes Association, WHO World Health Organization, NR Not reported.