The Association Between Body Mass Index and Pancreatic Cancer: Variation by Age at Body Mass Index Assessment

Higher body mass index (BMI; weight (kg)/height (m)2) is associated with increased risk of pancreatic cancer in epidemiologic studies. However, BMI has usually been assessed at older ages, potentially underestimating the full impact of excess weight. We examined the association between BMI and pancreatic cancer mortality among 963,317 adults who were aged 30–89 years at their enrollment in Cancer Prevention Study II in 1982. During follow-up through 2014, a total of 8,354 participants died of pancreatic cancer. Hazard ratios per 5 BMI units, calculated using proportional hazards regression, declined steadily with age at BMI assessment, from 1.25 (95% confidence interval: 1.18, 1.33) in persons aged 30–49 years at enrollment to 1.13 (95% confidence interval: 1.02, 1.26) in those aged 70–89 years at enrollment (P for trend = 0.005). On the basis of a hazard ratio of 1.25 per 5 BMI units at age 45 years, we estimated that 28% of US pancreatic cancer deaths among persons born in 1970–1974 will be attributable to BMI ≥25.0—nearly twice the equivalent proportion of those born in the 1930s, a birth cohort with much lower BMI in middle age. These results suggest that BMI before age 50 years is more strongly associated with pancreatic cancer risk than BMI at older ages, and they underscore the importance of avoiding excess weight gain before middle age for preventing this highly fatal cancer.