Association between alcohol consumption and the risk of incident type 2 diabetes: a systematic review and dose-response meta-analysis

Background: Previous cohort studies have shown that moderate alcohol consumption was associated with a lower risk of type 2 diabetes (T2D). However, whether these associations differ according to the characteristics of patients with T2D remains controversial. Objective: The purpose of this study was to explore and summarize the evidence on the strength of the association between alcohol consumption and the subsequent risk of T2D by using a dose-response meta-analytic approach. Design: We identified potential studies by searching the PubMed, Embase, and Cochrane Library databases up to 24 March 2015. Prospective observational studies that evaluated the relation between alcohol consumption and the risk of T2D and reported its effect estimates with 95% CIs were included. Results: Analyses were based on 706,716 individuals (275,711 men and 431,005 women) from 26 studies with 31,621 T2D cases. We detected a nonlinear relation between alcohol consumption and the risk of T2D, which was identified in all cohorts (P-trend < 0.001, P-nonlinearity < 0.001), in men (P-trend < 0.001, P-nonlinearity < 0.001), and in women (P-trend < 0.001, P-nonlinearity < 0.001). Compared with the minimal category of alcohol consumption, light (RR: 0.83; 95% CI: 0.73, 0.95; P = 0.005) and moderate (RR: 0.74; 95% CI: 0.67, 0.82; P < 0.001) alcohol consumption was associated with a lower risk of T2D. However, heavy alcohol consumption had little or no effect on subsequent T2D risk. Furthermore, the summary RR ratio (RRR; male to female) of the comparison between moderate alcohol consumption and the minimal alcohol categories for T2D was significantly higher, and the pooled RRR (current smoker to never smoker) of light alcohol consumption was significantly reduced. Conclusions: Light and moderate alcohol consumption was associated with a lower risk of T2D, whereas heavy alcohol consumption was not related to the risk of T2D.