Type 2 diabetes mellitus and risk of oral cancer and precancerous lesions: A meta-analysis of observational studies

Objective: Associations between type 2 diabetes mellitus (type 2 DM) and risk of oral cancer and precancerous lesions have been reported with controversial findings. We performed a meta-analysis to explore these associations. Methods: We identified studies by a literature search of MEDLINE and EMBASE through May 31, 2014, and by searching the reference lists of pertinent articles. Summary relative risk (SRR) with 95% confidence interval (CI) was calculated with a random-effects model. Between-study heterogeneity was assessed using the Cochran's Q and I-2 statistics. Results: A total of 13 studies (4 case-control and 9 cohort studies) on the association between type 2 DM and oral cancer were included. Overall analysis found that compared with non-diabetic individuals, individuals with type 2 DM had a significantly elevated incidence of oral cancer (SRR = 1.15, 95% CI: 1.02-1.29; P-heterogeneity = 0.277, I-2 = 15.4%; 10 studies). Subgroup analyses found that duration of follow-up (>= 11 years) significantly altered this positive association. Type 2 DM was associated with increased oral cancer mortality (SRR = 1.41, 95% CI: 1.16-1.72; 4 studies). Meta-analysis of the four case-control studies showed a positive association between type 2 DM and risk of oral precancerous lesions (SRR = 1.85, 95% CI: 1.23-2.80; P-heterogeneity = 0.038, I-2 = 57.5%). No significant public bias was found across these studies. Conclusions: These findings of this meta-analysis indicate that compared with non-diabetic individuals, individuals with type 2 DM have an elevated risk of oral cancer and precancerous lesions development. (C) 2015 Elsevier Ltd. All rights reserved.