It is well-documented that the dysregulation of trace elements may be involved in the pathogenesis of asthma. However, the precise changes of trace elements levels in asthma cases remain elusive. We established whether trace elements levels were associated with asthma susceptibility by pooling case-control studies.

34 studies were included. We extracted the standard mean differences (SMDs) and corresponding 95% confidence intervals (CIs). A pooled-analysis was performed.

No marked difference (95% CI: -1.437–0.218, p = 0.149) of Se level between asthma and controls. Significant difference (95% CI: 0.112–1.032, p = 0.015; 95% CI: 0.376–1.331, p < 10⁻⁴) of Cu level between asthma and controls was noted among overall populations and Asians. No marked difference of Zn level between asthma and controls was observed among overall populations, Asians, Caucasians and Africans. Significant difference (95% CI: -0.567 to −0.238, p < 10⁻⁴) of Mg level between asthma and controls was noted among Asians. Marked difference (95% CI: 0.258–2.864, p = 0.019; 95% CI: 0.270–3.282, p = 0.021) of Fe level between asthma and controls was noted among overall populations and Asians. Age had no impact on the pooled SMDs of Se, Cu, Zn, Mg and Fe between asthma and controls. Sensitivity analyses did not change the overall results. No publication bias was noted for overall populations.

Alterations of Cu, Mg and Fe levels may be a biomarker of asthma risk among specific populations. Further studies should be performed to clarify the strength of these elements in asthma.