Body mass index, physical activity and the risk of pancreatic cancer in relation to smoking status and history of diabetes: a large-scale population-based cohort study in Japan - The JPHC study

Objective: The effects of BMI and physical activity on the risk of pancreatic cancer were investigated in a large population-based cohort study in Japan (JPHC study). In particular, we explored how these effects were influenced by smoking status and a history of diabetes. Methods: In total, 99,670 participants (47,499 men, and 52,171women) were followed for an average of 11 years through the end of 2003. Hazard ratios (HR) and their 95% confidence intervals (CI) were estimated by Cox proportional hazards models. Results: A total of 224 incident cases (128 men, 96 women) of pancreatic cancer were identified. A statistically significant excess risk of pancreatic cancer was associated with current smoking (HR = 1.8, CI 1.1-3.0) and a history of diabetes (HR = 2.1, CI 1.3-3.5) among men. A similar increase in risk associated with current smoking (HR = 2.0, CI 0.9-4.4) and diabetes (HR = 1.5, CI 0.7-3.5) was also seen among women. BMI was inversely associated with risk of pancreatic cancer among men, especially among current male smokers or diabetes patients, but no association was found among women. Leisure-time physical activity was not associated with risk in either men or women. Conclusions: Our study confirms the association between cigarette smoking, history of diabetes and increased risk of pancreatic cancer. However, our data suggest that the association between BMI and risk of pancreatic cancer in this Japanese population may be different from that in Western populations.