Table 3.
Subgroup analyses of circulating zinc with risk of asthma and wheezing
| Subgroups | N | SMD | 95% CI | p | I2 |
|---|---|---|---|---|---|
| By ethnicity | |||||
| African | 3 | −0.23 | (−0.57, 0.11) | 0.188 | 40.2% |
| Caucasian | 3 | −0.41 | (−0.91, 0.10) | 0.213 | 35.4% |
| Middle Eastern | 15 | −0.42 | (−0.69, −0.14) | <0.001 | 87.1% |
| By the feature of case | |||||
| Asthma | 18 | −0.41 | (−0.65, −0.16) | <0.001 | 83.7% |
| Wheezing | 3 | −0.20 | (−0.58, 0.17) | 0.072 | 69.1% |
| Diagnosis of asthma | |||||
| Doctor | 12 | −0.30 | (−0.61, 0.01) | <0.001 | 85.7% |
| GINA | 6 | −0.58 | (−0.97, −0.19) | <0.001 | 77.7% |
| Non-GINA | 3 | −0.35 | (−0.87, 0.16) | 0.013 | 77.0% |
| By the source of controls | |||||
| Hospital | 14 | −0.46 | (−0.79, −0.13) | <0.001 | 88.1% |
| Population | 7 | −0.34 | (−0.48, −0.20) | 0.436 | 0.0% |
| By blood sample | |||||
| NA | 2 | −0.79 | (−2.30, 0.73) | <0.001 | 93.2% |
| Plasma | 4 | −0.15 | (−0.50, 0.20) | 0.237 | 29.1% |
| Serum | 15 | −0.37 | (−0.61, −0.17) | <0.001 | 83.6% |
| By detection technology | |||||
| AAS | 12 | −0.48 | (−0.77, −0.19) | <0.001 | 82.4% |
| NA | 3 | −0.18 | (−0.43, 0.07) | 0.418 | 0.0% |
| Non-AAS | 6 | −0.28 | (−0.78, 0.23) | <0.001 | 89.8% |
| By fasting status | |||||
| Fasting | 5 | −0.12 | (−0.30, 0.06) | 0.274 | 22.0% |
| NA | 15 | −0.49 | (−0.79, −0.20) | <0.001 | 85.3% |
| Non-fasting | 1 | −0.19 | (−0.63, 0.25) | NA | NA |
| By matched | |||||
| NA | 5 | −0.47 | (−1.05, 0.12) | <0.001 | 89.5% |
| Yes | 16 | −0.36 | (−0.60, −0.12) | <0.001 | 80.5% |
N number of included studies, SMD standardized mean difference, I2 percentage of total variation across studies, CI confidence interval, GINA Global Initiative for Asthma, Non-GINA refers to ERS/ATS and ISAAC, AAS atomic absorption spectrometry, NA not available