Body mass index, effect modifiers, and risk of pancreatic cancer: a pooled study of seven prospective cohorts

To investigate whether the positive association of body mass index (BMI, kg/m(2)) with risk of pancreatic cancer is modified by age, sex, smoking status, physical activity, and history of diabetes. In a pooled analysis of primary data of seven prospective cohorts including 458,070 men and 485,689 women, we identified 2,454 patients with incident pancreatic cancer during an average 6.9 years of follow-up. Cox proportional hazard regression models were used in data analysis. In a random-effects meta-analysis, for every 5 kg/m(2) increment in BMI, the summary relative risk (RR) was 1.06 (95% confidence interval (CI) 0.99-1.13) for men and 1.12 (95% CI 1.05-1.19) for women. The aggregate analysis showed that compared with normal weight (BMI: 18.5 to < 25), the adjusted RR was 1.13 (95% CI 1.03-1.23) for overweight (BMI: 25 to < 30) and 1.19 (95% CI 1.05-1.35) for obesity class I (BMI: 30 to < 35). Tests of interactions of BMI effects by other risk factors were not statistically significant. Every 5 kg/m(2) increment in BMI was associated with an increased risk of pancreatic cancer among never and former smokers, but not among current smokers (P-interaction = 0.08). The present evidence suggests that a high BMI is an independent risk factor of pancreatic cancer.