Table 1. Summary of the 20 observational studies included in the present meta-analysis.
| Study | Location | Design | Study population | No. of subjects | No. of DM (%) | Age, yr, mean or median | Selenium concentration, mean or median | Selenium measurement | Selenium classification |
|---|---|---|---|---|---|---|---|---|---|
| Yuan et al. (2018) [24] | China | Cross-sectional | Population based | 2,078 | 1,039 (50) | Controls: 62.8 | Controls: 61.7 | Blood, μg/L | Quartile |
| 1:1 match | Cases: 62.9 | Cases: 64.3 | |||||||
| Kohler et al. (2018) [18] | USA | Cross-sectional | Population based | 1,727 | 172 (10) | 63.1 | 139.8 | Blood, μg/L | Tertile |
| Li et al. (2017) [19] | China | Cross-sectional | Population based | 551 | 122 (22.1) | 66.4 | 16.4 | Blood, μg/L | Tertile |
| Galan-Chilet et al. (2017) [25] | Spain | Cross-sectional | Population based | 1,,452 | 120 | 49 | 84.2 | Blood, μg/L | Tertile |
| Hansen et al. (2017) [22] | Norway | Cross-sectional | Population based | 883 | 128 | Controls: 61.4 | Controls: 101.4a | Blood, μg/L | Quartile |
| Cases: 65.2 | Cases: 101.2a | ||||||||
| Zhang et al. (2017) [27] | China | Cross-sectional | Population based | 1,837 | 510 | Controls: 55.2 | Controls: 200 | Blood, μg/L | Quartile |
| Cases: 57.7 | Cases: 210 | ||||||||
| Skalnaya et al. (2017) [28] | Russia | Cross-sectional | Population based | 128 | 64 (50) | Controls: 56.7 | Controls: 110.2 | Blood, μg/L | Median |
| Menopausal women | 1:1 match | Cases: 55.8 | Cases: 126.8 | ||||||
| Lu et al. (2016) [29] | Taiwan | Cross-sectional | Hospital, 40 yr or older | 847 | 303 (35.8) | 63.9 | 86.7a | Blood, μg/L | Quartile |
| 1:2 match | |||||||||
| Alehagen et al. (2016) [30] | Sweden | Cross-sectional | Population based | 668 | 146 | NA | 67.1 | Blood, μg/L | Quartile |
| 70–80 yr | |||||||||
| Gao et al. (2014) [23] | Sweden | Cohort | Population based | 1,539 | 53 (for 10 yr) | 49.7 | 75.6 | Blood, μg/L | Tertile |
| Stranges et al. (2011) [31] | Italy | Cross-sectional | Population based | 445 | 13 | 50.9 | 77.5 | Blood, μg/L | Tertile |
| Laclaustra et al. (2009) [20] | USA | Cross-sectional | Population based | 917 | 121 | 54.2 | 137.1 | Blood, μg/L | Quartile |
| Bleys et al. (2007) [32] | USA | Cross-sectional | Population based | 8,876 | 1,379 | Controls: 42.8 | Controls: 125.7 | Blood, μg/L | Quintile |
| Cases: 58.3 | Cases: 126.5 | ||||||||
| Su et al. (2016) [33] | China | Cross-sectional | Population based | 1,856 | 163 | 74 | 0.461a | Nail, μg/g | Quartile |
| 65 yr or older | |||||||||
| Vinceti et al. (2015) [34] | Italy | Cross-sectional | Population based | 621 | 226 | Controls: 50.9 | 0.57 | Nail, μg/g | Quartile |
| Women, 35–70 yr | Cases: 51.2 | ||||||||
| Park et al. (2012) [21] | USA | Cohort | Population based | Men: 3,535 | 780 | Men: 59.6 | Men: 0.84 | Nail, μg/g | Quintile |
| Nurses, 30–55 yr | Women: 3,630 | Women: 52.6 | Women: 0.77 | ||||||
| Health professional, 40–75 yr | |||||||||
| Liu et al. (2016) [35] | China | Cross-sectional | The coke oven workers | 1,493 | 102 | Controls: 41.8 | Controls: 10 | Urine, μg/L | Tertile |
| Cases: 47 | Cases: 11.5 | ||||||||
| Feng et al. (2015) [36] | China | Cross-sectional | Population based | 2,242 | 218 | 53 | 7.42a | Urine, μg/L | Quartile |
| Wei et al. (2015) [37] | China | Cross-sectional | Population based | 5,423 | 525 | Controls: 52.9 | Controls: 43.2 | Intake, μg/day | Quartile |
| 40 yr or older | Cases: 54.7 | Cases: 46.8 | |||||||
| Stranges et al. (2010) [39] | Italy | Cohort | Population based | 7,182 | 253 | Controls: 47.1 | Controls: 56.8 | Intake, μg/day | Quintile |
| Healthy women, 34–70 yr | Cases: 51.2 | Cases: 60.9 |
QuintileDM, diabetes mellitus; NA, not available.
aMedian.