Risk of esophageal cancer in diabetes mellitus: a meta-analysis of observational studies

Objective Inconsistent findings from observational studies have prolonged the controversy over the effects of history of diabetes mellitus (DM) on the risk of esophageal cancer (EC). We conducted a meta-analysis of epidemiologic studies to evaluate the association of a history of DM with the risk of EC. Methods We identified studies by a literature search of MEDLINE (from 1 January 1966) and EMBASE (from 1 January 1974), through 28 Feburary 2011, and by searching the reference lists of pertinent articles. Summary relative risks (SRRs) with 95% confidence intervals (CIs) were calculated with a random-effects model. All statistical tests were two-sided. Results A total of 17 studies (6 case-control studies and 11 cohort studies) fulfilled the inclusion and exclusion criteria. Compared with non-diabetic individuals, diabetic individuals had a modestly increased risk of EC (SRRs 1.30, 95% CI: 1.12-1.50), with significant heterogeneity among studies (p = 0.042). In stratified analysis, the SRRs of EC were 1.28 (1.10-1.49) for diabetic men and 1.07 (95% CI, 0.71-1.62) for diabetic women, respectively. In addition, DM was associated with an increased risk of esophageal adenocarcinoma (SRR 2.12, 95% CI 1.01-4.46). There was no significant publication bias (p = 0.127 for Begg's adjusted rank correlation test and p = 0.629 for Egger's regression test). Conclusion These findings support the hypothesis that men with diabetes may have a modestly increased risk of EC, while diabetic women were not the case.