This meta-analysis was conducted aiming to summarize the results obtained from the previous studies so that the effect of opium on blood lead levels (BLLs) can be investigated. Scopus, Embase, PubMed, and Web of Science (ISI) were systematically searched up to June 2020. Heterogeneity of the included studies was evaluated using Cochrane's Q test and the I2 statistic. A random-effects model was used to pool the weighted mean differences (WMDs) and their 95% confidence intervals (CIs). Out of a total of 2372 citations, eleven articles with 916 participants (487 opium addicts and 429 controls) were included in the study. The meta-analysis results showed that there were higher lead levels (WMD = 14.59 μg/dL, 95% CI = 11.59 to 17.92, Z = 8.60, P < 0.001) in opium addicts than in the control group. The degree of heterogeneity observed (P < 0.001, I2 = 98.1%) might be mainly the result of the type of sampling and of consumption. Moreover, the findings of meta-regression analyses indicated that publication year (β = 1.23, P = 0.287), total sample size (β = 0.05, P = 0.728), and quality scores (β = - 2.91, P = 0.546) had no effects on lead levels in opium addicts. In the sensitivity analysis, it was found that the pooled WMDs remained stable after excluding one by one study. Oral opium consumption increased the amount of lead in the bloodstream, and the measurement of lead levels in opium addicts' blood may be regarded as a useful test to diagnosis and prognosis of disorders that may lead poisoning causes.
Keywords: Lead; Meta-analysis; Opium; Systematic review.
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