Background Moderate alcohol consumption is associated with a decreased risk of type 2 diabetes. However, the relationship between drinking patterns, such as the weekly frequency of alcohol consumption and the quantity per drinking day, and the incidence of type 2 diabetes has not been sufficiently addressed.

Methods Study participants included 10 631 Japanese men aged 40–55 years without type 2 diabetes at entry. Type 2 diabetes was diagnosed if a fasting plasma glucose level was ≥7.0 mmol/l or if participants were taking diabetes medications. Data on alcohol consumption were obtained from questionnaires.

Results During the 37 172 person-years of follow-up, we confirmed 878 cases of type 2 diabetes. Frequent alcohol consumption was associated with a low risk of type 2 diabetes. Compared to non-drinkers, the multiple-adjusted HR for those who drank 4–7 days weekly was 0.76 (95% CI, 0.63 to 0.92). To assess the association between drinking pattern and type 2 diabetes, we examined the joint association of the weekly frequency and the quantity per drinking day with type 2 diabetes. Men who consumed 0.1–2.0 or 2.1–4.0 US standard drinks per drinking day on 4–7 days weekly had a lower risk of type 2 diabetes (HR 0.74, 95% CI 0.58 to 0.95; HR 0.74, 95% CI 0.60 to 0.91, respectively) compared to non-drinkers.

Conclusions More frequent alcohol consumption lowered the risk of type 2 diabetes. Light to moderate alcohol consumption per drinking day on 4–7 days weekly lowered the risk of type 2 diabetes compared to non-drinkers.