Prevention of Keshan Disease by Selenium Supplementation: a Systematic Review and Meta-analysis.

Systematic review (SR) of high-quality studies provides superior evidence, but an SR has not been conducted to evaluate the association between Keshan disease (KD) and selenium deficiency because SR was not available when KD was highly prevalent in the 1950s to 1970s. The objective of this study was to update our understanding of the etiology of KD and provide evidence for policies and strategies in KD surveillance, prevention, and control. We identified related studies by searching the CNKI, Wanfang, CQVIP, SinoMed, CMCI, PubMed, Embase, and EBSCO databases from January 1935 to April 2017. Community trials that met the inclusion criteria were included. Risk ratios (RR) with corresponding 95% confidence intervals (CI) were pooled to compare incidences between the two groups. A total of 17 articles (including 41 studies) were included. In total, the studies included 1,983,238 subjects, 683,075 of which were in experimental groups and 1,300,163 of which were in control groups. The protection rates were over 80% in 35 studies, and the overall effect (risk ratio) was 0.14 [95% CI (0.12, 0.16), P < 0.05]. Potential publication bias was observed in the funnel plots, but the results of Egger's and Begg's tests showed that there was no evidence of publication bias. Giving selenium supplements to the residents of KD endemic areas significantly reduced the incidence of KD. Selenium deficiency is therefore a cause of KD by the criterion of causation in modern epidemiology. Selenium should be included in the KD surveillance program. The description of "unknown cause" in the definition of KD may be inappropriate.