A prospective study of folate, vitamin B₆, and vitamin B₁₂ intake in relation to exfoliation glaucoma or suspected exfoliation glaucoma.

IMPORTANCE: Effective strategies for primary prevention are lacking for exfoliation glaucoma (EG), which is the most common type of secondary glaucoma.
OBJECTIVE: To examine the association between B vitamin intake and EG or suspected EG (EG/SEG) risk. DESIGN, SETTING, AND PARTICIPANTS: National prospective cohort study using more than 20 years of follow-up data from the Nurses' Health Study (all female registered nurses) and the Health Professionals Follow-up Study (all male health professionals) from June 1, 1980, to May 31, 2010 (Nurses' Health Study) and January 1, 1986, to December 31, 2010 (Health Professionals Follow-up Study). We included a subset of 78,980 Nurses' Health Study women and 41,221 Health Professionals Follow-up Study men who were 40 years or older, free of glaucoma, had completed diet questionnaires, and reported eye examinations (follow-up rate, >85%). EXPOSURES: Cumulatively updated intake of B vitamins (folate, vitamin B6, and vitamin B12) as ascertained by repeated administration of validated questionnaires. MAIN OUTCOMES AND MEASURES: Incident cases of EG/SEG, totaling 399 (329 women and 70 men), were first identified with the questionnaires and were subsequently confirmed with medical records. Multivariable relative risks for EG/SEG were calculated in each cohort and then pooled with meta-analysis.
RESULTS: Vitamin B₆ and vitamin B₁₂ intake was not associated with EG/SEG risk in pooled analyses (P = .52 and P = .99 for linear trend, respectively). However, a suggestive trend of a reduced risk was observed with higher intake of folate: compared with the lowest quintile of cumulatively averaged updated total folate intake, the multivariable relative risk for EG/SEG for the highest quintile (≥654 μg/d) was 0.75 (95% CI, 0.54-1.04; P = .02 for linear trend). These results were not materially altered after adjustment for vitamin B₆ and vitamin B₁₂ intake. An association was observed for supplemental folate intake but not for dietary folate only (P = .03 and P = .64 for linear trend, respectively). Greater frequency of multivitamin use showed a modest suggestive inverse association (current multivitamin use of ≥6 times per week vs nonuse multivariable relative risk, 0.84; 95% CI, 0.64-1.11; P = .06 for linear trend). CONCLUSIONS AND RELEVANCE: Higher total folate intake was associated with a suggestive lower risk for EG/SEG, supporting a possible causal role of homocysteine in EG/SEG.