Predicted vitamin D status and pancreatic cancer risk in two prospective cohort studies

BACKGROUND: Studies evaluating vitamin D status in relation to pancreatic cancer risk have yielded inconsistent results. METHODS: We prospectively followed 118 597 participants in the Nurses' Health Study and Health Professionals Follow-up Study from 1986 to 2006. We calculated a 25-hydroxyvitamin D (25(OH)D) score from known predictors of vitamin D status for each individual and then examined the predicted 25(OH)D levels in relation to pancreatic cancer risk. Relative risks (RRs) and 95% confidence intervals (95% CIs) were estimated using Cox proportional hazards models adjusted for age, sex, race, height, smoking, and diabetes. We then further adjusted for body mass index (BMI) and physical activity in a sensitivity analysis. RESULTS: During 20 years of follow-up, we identified 575 incident pancreatic cancer cases. Higher 25(OH)D score was associated with a significant reduction in pancreatic cancer risk; compared with the lowest quintile, participants in the highest quintile of 25(OH)D score had an adjusted RR of 0.65 (95% CI=0.50-0.86; P(trend)=0.001). Results were similar when we further adjusted for BMI and physical activity. CONCLUSIONS: Higher 25(OH)D score was associated with a lower risk of pancreatic cancer in these two prospective cohort studies.