Abstract and Introduction
Background Dietary pattern analyses characterizing combinations of food intakes offer conceptual and statistical advantages over food- and nutrient-based analyses of disease risk. However, few studies have examined dietary patterns and pancreatic cancer risk and none focused on the 2005 Dietary Guidelines for Americans. We used the Healthy Eating Index 2005 (HEI-2005) to estimate the association between meeting those dietary guidelines and pancreatic cancer risk.
Methods We calculated the HEI-2005 score for 537 218 men and women in the National Institutes of Health–American Association of Retired Persons Diet and Health Study using responses to food frequency questionnaires returned in 1995 and 1996. We used Cox proportional hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of pancreatic cancer according to HEI-2005 quintiles and explored effect modification by known risk factors. P interaction values were calculated using the Wald test. All statistical tests were two-sided.
Results We identified 2383 incident, exocrine pancreatic cancer cases (median = 10.5 years follow-up). Comparing participants who met the most dietary guidelines (Q5) with those who met the fewest guidelines (Q1), we observed a reduced risk of pancreatic cancer (HR = 0.85, 95% CI = 0.74 to 0.97). Among men there was an interaction by body mass index (P interaction = .03), with a hazard ratio of 0.72 (95% CI = 0.59 to 0.88) comparing Q5 vs Q1 in overweight/obese men (body mass index ≥25kg/m2) but no association among normal weight men.
Conclusions Our findings support the hypothesis that consuming a high-quality diet, as scored by the HEI-2005, may reduce the risk of pancreatic cancer.
Pancreatic cancer is one of the most rapidly fatal cancers and is the fourth leading cause of cancer death in the United States.[1,2] Although most food- and nutrient-based analyses have shown weak or no associations with pancreatic cancer,[3,4] dietary pattern analysis may better predict disease risk than individual food or nutrient intakes for several reasons. First, high correlation between nutrients may be difficult to unravel statistically. Second, there may be biologic interaction or synergy between different nutrients and/or dietary constituents/components that is not captured when assessing single foods or nutrients. Third, diet-related associations with disease may be easier to detect when comparing overall diets of poor or high quality rather than intake of an isolated food or nutrient.[6,7]
The few studies on dietary patterns and pancreatic cancer risk have shown inconsistent results[8–13] and used different statistical methods that reflect distinct research questions. All but one of the previous studies examined data-driven, study-specific dietary patterns, preventing comparison between studies. A priori patterns, on the other hand, may be compared between studies because they are characterized based on disease-specific biologic rationale or public health guidance. One such a priori pattern is the Dietary Guidelines for Americans 2005, which can be measured using the Healthy Eating Index 2005 (HEI-2005). These guidelines were the basis of federal nutrition policy and nutrition education activities from 2005 to 2010. Thus, associations between this dietary pattern and disease risk have nationally relevant public health implications.
To our knowledge, no previous studies have assessed the HEI-2005 and pancreatic cancer risk. Also, most previous dietary pattern and pancreatic cancer studies lack sufficient case subjects to fully explore effect modification. Given these identified gaps in the literature, we tested the association between the HEI-2005 score and pancreatic cancer risk in the large, prospective National Institutes of Health (NIH)–AARP (formerly known as the American Association of Retired Persons) Diet and Health Study cohort.
J Natl Cancer Inst. 2013;105(17):1298-1305. © 2013 Oxford University Press