Table 3.
Subgroup meta-analysis of heavy metal exposure and risk of metabolic syndrome
| Variable | Sub-grouped by | No. of arms | Pooled effect size | 95% CI | I2 (%) | P for heterogeneity | |
|---|---|---|---|---|---|---|---|
| Overall-heavy metals | gender | Both | 24 | 1.39 | 1.064,1.22* | 73.9 | < 0.001 |
| Male | 12 | 1.37 | 1.14,1.65* | 48.9 | 0.028 | ||
| Female | 10 | 0.96 | 0.72,1.29 | 82.0 | < 0.001 | ||
| Age | Senior Adult (> 50) | 13 | 1.04 | 0.90,1.20 | 66.0 | < 0.001 | |
| Middle-aged Adult (30–50) | 26 | 1.20 | 1.10,1.30* | 79.0 | < 0.001 | ||
| young adult (20–30) | 7 | 1.21 | 0.79,1.83 | 71.6 | 0.002 | ||
| Study design | Cross-sectional | 44 | 1.15 | 1.08,1.22* | 75.0 | < 0.001 | |
| Case–control | 2 | 1.99 | 1.16,3.44* | 0.0 | 0.725 | ||
| region | Asia | 40 | 1.19 | 1.10,1.27 | 75.9 | < 0.001 | |
| Europe | 4 | 0.88 | 0.55,1.41 | 77.1 | < 0.001 | ||
| USA | 2 | 0.98 | 0.74,1.30 | 75.9 | < 0.001 | ||
| Sample size | 1500 > = | 20 | 1.09 | 0.97,1.23 | 68.6 | < 0.001 | |
| 1500–4000 | 17 | 1.26 | 1.09,1.44 | 75.1 | < 0.001 | ||
| > 4000 | 9 | 1.15 | 0.99,1.35 | 82.1 | < 0.001 | ||
| Cadmium | gender | Both | 7 | 1.15 | 1.003,1.31* | 53.7 | 0.043 |
| Male | 4 | 1.72 | 1.005,2.93* | 51.6 | 0.103 | ||
| Female | 2 | 1.41 | 0.20,6.85 | 91.3 | 0.001 | ||
| Age | Senior Adult (> 50) | 3 | 1.23 | 1.03,1.45* | 0.0 | 0.642 | |
| Middle-aged Adult (30–50) | 8 | 1.19 | 0.99,1.47 | 70.3 | 0.001 | ||
| young adult (20–30) | 2 | 2.6 | 0.94,7.15 | 41.5 | 0.191 | ||
| Study design | Cross-sectional | 12 | 1.21 | 1.03,1.42 | 64.7 | 0.001 | |
| Case–control | 1 | 2.2 | 1.03,4.71 | 0.0 | – | ||
| Lead | gender | Both | 9 | 1.11 | 0.95,1.30 | 69.9 | 0.001 |
| Male | 4 | 1.18 | 1.03,1.35* | 0.0 | 0.705 | ||
| Female | 4 | 0.69 | 0.42,1.14 | 83.3 | < 0.001 | ||
| Age | Senior Adult (> 50) | 6 | 0.92 | 0.74,1.14 | 76.2 | 0.001 | |
| Middle-aged Adult (30–50) | 8 | 1.14 | 0.95,1.36 | 70.7 | 0.001 | ||
| young adult (20–30) | 3 | 1.08 | 0.53,2.23 | 44.7 | 0.164 | ||
| Study design | Cross-sectional | 16 | 1.04 | 0.92,1.18 | 69.6 | < 0.001 | |
| Case–control | 1 | 1.81 | 0.83,3.93 | – | – | ||
| Mercury | gender | Both | 8 | 1.20 | 1.03,1.40* | 83.6 | < 0.001 |
| Male | 5 | 1.35 | 1.01,1.80* | 69.1 | 0.012 | ||
| Female | 4 | 1.07 | 0.72,1.60 | 78.4 | 0.003 | ||
| Age | Senior Adult (> 50) | 5 | 1.16 | 0.92,1.48 | 65.4 | 0.021 | |
| Middle-aged Adult (30–50) | 10 | 1.31 | 1.11,1.54* | 86.6 | < 0.001 | ||
| young adult (20–30) | 2 | 0.78 | 0.54,1.11 | 0.0 | 0.862 | ||
| Cooper | gender | Both | 4 | 1.23 | 0.88,1.74 | 81.2 | 0.001 |
| Male | 3 | 1.30 | 0.64,2.62 | 77.0 | 0.013 | ||
| Female | 1 | 1.28 | 0.81,2.01 | – | – | ||
| Age | Senior Adult (> 50) | 5 | 1.12 | 0.83,1.52 | 57.9 | 0.05 | |
| Middle-aged Adult (30–50) | 3 | 1.52 | 0.86,2.70 | 87.3 | < 0.001 | ||
| Study design | Cross-sectional | 4 | 1.25 | 0.87,1.81 | 80.7 | 0.001 | |
| Case–control | 4 | 1.25 | 0.80,1.96 | 69.3 | 0.021 | ||
| Manganese | gender | Both | 4 | 1.12 | 0.82,1.51 | 65.9 | 0.032 |
| Male | 2 | 0.84 | 0.36,1.93 | 68.8 | 0.074 | ||
| Female | 1 | 0.89 | 0.45,1.76 | – | – | ||
| Age | Senior Adult (> 50) | 1 | 1.19 | 0.79,1.77 | – | – | |
| Middle-aged Adult (30–50) | 6 | 1.02 | 0.77,1.35 | 59.3 | 0.031 | ||
| Iron | gender | Both | 5 | 1.56 | 1.03,2.37* | 77.0 | 0.002 |
| Male | 3 | 0.88 | 0.67,1.16 | 0.0 | 0.574 | ||
| Female | 2 | 1.14 | 0.23,5.67 | 95.2 | < 0.001 | ||
| Age | Senior Adult (> 50) | 6 | 1.50 | 0.90,2.49 | 82.8 | < 0.001 | |
| Middle-aged Adult (30–50) | 4 | 0.96 | 0.59,1.58 | 83.7 | < 0.001 | ||
| Study design | Cross-sectional | 4 | 1.19 | 0.73,1.95 | 76.7 | 0.005 | |
| Cohort | 2 | 0.64 | 0.41,1.01 | 54.2 | 0.140 | ||
| Case–control | 4 | 1.85 | 1.16,2.94* | 73.3 | 0.011 | ||