Caffeine consumption and the risk of primary open-angle glaucoma: a prospective cohort study.

PURPOSE To investigate whether caffeine, which transiently increases intraocular pressure (IOP) is associated with the risk of primary open-angle glaucoma (POAG). METHODS A total of 79,120 women from 1980 to 2004 and 42,052 men from 1986 to 2004, who were 40+ years of age, did not have POAG, and reported undergoing eye examinations, were observed. Information on caffeine consumption, potential confounders, and POAG diagnoses were repeatedly updated in validated follow-up questionnaires. One thousand eleven incident POAG cases were confirmed with medical record review. Cohort-specific and pooled analyses across cohorts were conducted to calculate multivariate rate ratios (RRs). RESULTS Compared with daily intake of less than 150 mg, the pooled multivariate RRs were 1.05 (95% confidence interval [CI], 0.89-1.25) for consumption of 150 to 299 mg/d, 1.19 (95% CI, 0.99-1.43) for 300 to 449 mg/d, 1.13 (95% CI, 0.89-1.43) for 450 to 559 mg/d, and 1.17 (95% CI, 0.90-1.53) for 600+ mg/d (P for trend = 0.11). However, for consumption of five or more cups of caffeinated coffee daily, the RR was 1.61 (95% CI, 1.00-2.59; P for trend = 0.02); tea or caffeinated cola intake were not associated with risk. Greater caffeine intake was more adversely associated with POAG among those reporting a family history of glaucoma, particularly in relation to POAG with elevated IOP (P for trend = 0.0009; P interaction = 0.04). CONCLUSIONS Overall caffeine intake was not associated with increased risk of POAG. However, in secondary analyses, caffeine appeared to elevate risk of high-tension POAG among those with a family history of glaucoma. This result may be due to chance, but warrants further study.