Context: Diabetes mellitus and elevated postload plasma glucose levels have been associated with an increased risk of pancreatic cancer in previous studies. By virtue of their influence on insulin resistance, obesity and physical inactivity may increase risk of pancreatic cancer.
Objective: To examine obesity, height, and physical activity in relation to pancreatic cancer risk.
Design and setting: Two US cohort studies conducted by mailed questionnaire, the Health Professionals Follow-up Study (initiated in 1986) and the Nurses' Health Study (initiated in 1976), with 10 to 20 years of follow-up.
Participants: A total of 46 648 men aged 40 to 75 years and 117 041 women aged 30 to 55 years who were free of prior cancer at baseline and had complete data on height and weight.
Main outcome measures: Relative risk of pancreatic cancer, analyzed by self-reported body mass index (BMI), height, and level of physical activity.
Results: During follow-up, we documented 350 incident pancreatic cancer cases. Individuals with a BMI of at least 30 kg/m(2) had an elevated risk of pancreatic cancer compared with those with a BMI of less than 23 kg/m(2) (multivariable relative risk [RR], 1.72; 95% confidence interval [CI], 1.19-2.48). Height was associated with an increased pancreatic cancer risk (multivariable RR, 1.81; 95% CI, 1.31-2.52 for the highest vs lowest categories). An inverse relation was observed for moderate activity (multivariable RR, 0.45; 95% CI, 0.29-0.70 for the highest vs lowest categories; P for trend <.001). Total physical activity was not associated with risk among individuals with a BMI of less than 25 kg/m(2) but was inversely associated with risk among individuals with a BMI of at least 25 kg/m(2) (pooled multivariable RR, 0.59; 95% CI, 0.37-0.94 for the top vs bottom tertiles of total physical activity; P for trend =.04).
Conclusion: In 2 prospective cohort studies, obesity significantly increased the risk of pancreatic cancer. Physical activity appears to decrease the risk of pancreatic cancer, especially among those who are overweight.