Prospective study of flavonoid intake and risk of primary open-angle glaucoma

Purpose To evaluate the association between flavonoid intake and incident primary open-angle glaucoma (POAG). MethodsResultsWe followed 65516 women from the Nurses' Health Study (from 1984) and 42156 men from the Health Professionals Follow-up Study (from 1986) biennially to 2012, who were 40+ years old, free of POAG, and reported eye examinations. Dietary flavonoid intake was assessed with validated repeated semi-quantitative food frequency questionnaires. Incident POAG cases (n=1575) were confirmed with medical record review. Cohort-specific multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CIs) were calculated and meta-analysed. Total flavonoid intake was not associated with risk of POAG development [RR for highest (Q5: median similar to 645mg/day) versus lowest quintile (Q1: similar to 130mg/day)=0.91 (95% CI=0.77, 1.08); p for trend (p-trend)=0.19]; the flavonoid subclasses of flavones, flavanones, polymeric flavanols or anthocyanidins were also not associated (Q5 versus Q1 comparison p-values 0.05 and p-trend 0.09). Higher intakes of flavonols and monomeric flavanols were nominally associated with lower POAG risk, based on the Q5 versus Q1 comparisons or p-trends. The Q5 versus Q1 comparison RRs were: for flavonols, 0.82 (95% CI=0.69, 0.97; p-trend=0.05; similar to 28 versus similar to 8mg/day), and for monomeric flavanols, 0.86 (95% CI=0.72, 1.02; p-trend=0.04; similar to 110 versus 10mg/day). The food/beverage that contributed most to both the variation of flavonols and monomeric flavanols was tea; consuming similar to 2 cups/day was associated with 18% lower POAG risk (RR=0.82; 95% CI=0.68, 0.99; p-trend=0.02). ConclusionTotal flavonoid intake was not associated with POAG risk. Greater intakes of flavonols and monomeric flavanols and of tea showed suggestive modest associations with lower risk; these results need confirmation.