Shared and study-specific dietary patterns and head and neck cancer risk in an international consortium.

BACKGROUND: A few papers have considered reproducibility of a posteriori dietary patterns across populations, as well as pattern associations with head and neck cancer risk when multiple populations are available. METHODS: We used individual-level pooled data from seven case-control studies (3,844 cases; 6,824 controls) participating in the International Head and Neck Cancer Epidemiology consortium. We simultaneously derived shared and study-specific a posteriori patterns with a novel approach called multi-study factor analysis applied to 23 nutrients. We derived odds ratios (ORs) and 95% confidence intervals (CIs) for cancers of the oral cavity and pharynx combined, and larynx, from logistic regression models. RESULTS: We identified three shared patterns that were reproducible across studies (75% variance explained): the Anti-oxidant vitamins and fiber (OR=0.57, CI: 0.41-0.78, highest vs. lowest score quintile) and the Fats (OR=0.80, CI: 0.67-0.95) patterns were inversely associated with oral and pharyngeal cancer risk. The Animal products and cereals (OR=1.5, CI: 1.1-2.1) and the Fats (OR=1.8, CI: 1.4-2.3) patterns were positively associated with laryngeal cancer risk, whereas a linear inverse trend in laryngeal cancer risk was evident for the Anti-oxidant vitamins and fiber pattern. We also identified four additional study-specific patterns, one for each of the four US studies examined. We named them all as Dairy products and breakfast cereals and two were associated with oral and pharyngeal cancer risk. CONCLUSION: Multi-study factor analysis provides insight into pattern reproducibility, and supports previous evidence on cross-country reproducibility of dietary patterns and on their association with head and neck cancer risk.