Background The association between diabetes and gastric cancer has been rarely studied.

Objective To investigate gastric cancer mortality trends, the mortality rate ratios between patients with diabetes and the general population, and the risk factors for gastric cancer mortality in diabetic patients.

Methods In the Taiwanese general population from 1995 to 2006, age-standardised trends of gastric cancer mortality were evaluated, followed by calculation of age–sex-specific mortality rates. A total of 113 347 men with diabetes and 131 573 women with diabetes, aged ≥25 years and recruited in 1995–1998, were followed to 2006 for gastric cancer mortality. Age–sex-specific mortality rate ratios for diabetic patients versus the general population were calculated. Cox's regression was used to evaluate the risk factors among diabetic patients.

Results A decreasing trend of age-standardised gastric cancer mortality in the general population (p<0.0001) was observed from 1995 to 2006 for both sexes. A total of 627 diabetic men and 422 diabetic women died of gastric cancer, with a calculated mortality rate of 72.8 and 40.0 per 100 000 person-years, respectively. Mortality rate ratios showed a significantly higher risk in diabetic patients with a magnitude most remarkable at the youngest age: 1.52 (1.31–1.77), 1.58 (1.40–1.78) and 4.49 (3.93–5.12) for ≥75, 65–74 and 25–64 years old, respectively, for men; and 1.58 (1.32–1.90), 1.95 (1.67–2.27) and 3.65 (3.11–4.28), respectively, for women. In the diabetic patients, age and male sex were associated with gastric cancer mortality, but diabetes type, insulin use, and smoking were not. Body mass index and area of residence did not show consistent association. Diabetes duration was significantly predictive when those who died of gastric cancer within 5 years of diabetes diagnosis were excluded from analysis.

Conclusions Despite a decreasing age-standardised mortality trend in the general population, diabetic patients have a higher risk of gastric cancer mortality and this was most remarkable in the youngest age group of 25–64 years.