Physical activity, diet, and pancreatic cancer: a population-based, case-control study in Minnesota

Although mounting evidence suggests that insulin resistance is involved in pancreatic carcinogenesis, few epidemiologic studies have comprehensively investigated the role of lifestyle factors influencing this metabolic disorder in the etiology of pancreatic cancer. We sought to examine this problem in a case-control study conducted in 1994-1998 in Minnesota. Cases (n = 186), aged 20 yr or older, were ascertained from all hospitals in the metropolitan area of the Twin Cities and the Mayo Clinic; from the latter, only cases residing in the Upper Midwest of the United States were recruited. Controls (n = 554) were randomly selected from the general population and frequency matched to cases by age (within 5 yr) and sex. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using unconditional logistic regression. After adjustment for confounders, physical activity was associated with a reduced risk, but this protective effect was confined to light activity and moderate activity only (OR = 0.55, 95% CI = 0.30-0.97, P(trend) = 0.038 and OR = 0.51, 95% CI = 0.28-0.93, P(trend) = 0.07, for highest vs. lowest quartile, respectively). An increased risk was found for dietary intakes of energy and fat but was statistically significant for saturated and polyunsaturated fat only. Of note, no appreciable difference in the magnitude of the associations existed between saturated, monounsaturated, and polyunsaturated fat. Compared with individuals in the lowest quartile of fiber intake, the risk was approximately halved for those in the third (OR = 0.49, 95% CI = 0.26-0.94) and the highest quartile (OR = 0.52, 95% CI = 0.21-1.30). Our study lends support to the hypothesis that dietary and other lifestyle factors influencing insulin resistance modulate pancreatic cancer risk.