Investigating Physical Activity in the Etiology of Pancreatic Cancer: The Age at Which This Is Measured Is Important and Is Independent of Body Mass Index.

Abstract

There are plausible biological mechanisms for how increased physical activity (PA) may prevent pancreatic cancer, although findings from epidemiological studies are inconsistent. We investigated whether the risk is dependent on the age at which PA is measured and if independent of body mass index (BMI). A total of 23,639 participants, aged 40 to 74 years, were recruited into the EPIC-Norfolk (European Prospective Investigation of Cancer) cohort study between 1993 and 1997 and completed validated questionnaires on PA. The cohort was monitored for pancreatic cancer development, and hazard ratios (HRs) were estimated and adjusted for covariates. Within 17 years, 88 participants developed pancreatic cancer (55% female). There was no association between PA and risk in the cohort (HR trend, 1.06; 95% confidence interval [CI], 0.86-1.29). However, in participants younger than 60 years, higher PA was associated with decreased risk (highest vs lowest category HR, 0.27; 95% CI, 0.07-0.99). Higher PA was not inversely associated when older than 60 years (HR trend, 1.23; 95% CI, 0.96-1.57). Including BMI in all models produced similar estimates. The reasons why PA in younger, but not older, people may prevent pancreatic cancer need to be investigated. Physical activity may operate through mechanisms independent of BMI. If this association is causal, 1 in 6 cases might be prevented by encouraging more PA.