Context: Obesity has been implicated as a risk factor for pancreatic cancer.

Objective: To demonstrate the association of excess body weight across an age cohort and the risk, age of onset, and overall survival of patients with pancreatic cancer.

Design, setting, and participants: A case-control study of 841 patients with pancreatic adenocarcinoma and 754 healthy individuals frequency matched by age, race, and sex. The study was conducted at a university cancer center in the United States from 2004 to 2008. Height and body weight histories were collected by personal interview starting at ages 14 to 19 years and over 10-year intervals progressing to the year prior to recruitment in the study.

Main outcome measures: The associations between patients' body mass index (BMI) and risk of pancreatic cancer, age at onset, and overall survival were examined by unconditional logistic regression, linear regression, and Cox proportional hazard regression models, respectively.

Results: Individuals who were overweight (a BMI of 25-29.9) from the ages of 14 to 39 years (highest odds ratio [OR], 1.67; 95% confidence interval [CI], 1.20-2.34) or obese (a BMI > or = 30) from the ages of 20 to 49 years (highest OR, 2.58; 95% CI, 1.70-3.90) had an associated increased risk of pancreatic cancer, independent of diabetes status. The association was stronger in men (adjusted OR, 1.80; 95% CI, 1.45-2.23) by mean BMI from the ages of 14 to 59 years than in women (adjusted OR, 1.32; 95% CI, 1.02-1.70) and in ever smokers (adjusted OR, 1.75; 95% CI, 1.37-2.22) than in never smokers (adjusted OR, 1.46; 95% CI, 1.16-1.84). The population-attributable risk percentage of pancreatic cancer based on the mean BMI from the ages of 14 to 59 years was 10.3% for never smokers and 21.3% for ever smokers. Individuals who were overweight or obese from the ages of 20 to 49 years had an earlier onset of pancreatic cancer by 2 to 6 years (median age of onset was 64 years for patients with normal weight, 61 years for overweight patients [P = .02], and 59 years for obese patients [P < .001]). Compared with those with normal body weight and after adjusting for all clinical factors, individuals who were overweight or obese from the ages of 30 to 79 years or in the year prior to recruitment had reduced overall survival of pancreatic cancer regardless of disease stage and tumor resection status (overweight patients: hazard ratio, 1.26 [95% CI, 0.94-1.69], P = .04; obese patients: hazard ratio, 1.86 [95% CI, 1.35-2.56], P < .001).

Conclusions: Overweight or obesity during early adulthood was associated with a greater risk of pancreatic cancer and a younger age of disease onset. Obesity at an older age was associated with a lower overall survival in patients with pancreatic cancer.