Effective strategies for primary prevention are lacking for exfoliation glaucoma (EG), which is the most common type of secondary glaucoma. Massachusetts researchers examined the association between B vitamin intake and EG or suspected EG (EG/SEG) risk in this 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).
They 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 included cumulatively updated intake of B vitamins (folate, vitamin B6
and vitamin B12
) as ascertained by repeated administration of validated questionnaires. As for main outcome measures, the researchers first identified incident cases of EG/SEG, totaling 399 (329 women and 70 men), with the questionnaires and subsequently confirmed them with medical records. They also calculated multivariable relative risks for EG/SEG in each cohort and then pooled them with meta-analysis.
According to the researchers, vitamins B6
intake was not associated with EG/SEG risk in pooled analyses (p
=0.52 and p
=0.99 for linear trend, respectively). However, they observed a suggestive trend of a reduced risk 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 to 1.04; p
=0.02 for linear trend). These results were not materially altered after adjustment for vitamins B6
intake. The study researchers observed an association for supplemental folate intake, but not for dietary folate only (p
=0.03 and p
=0.64 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 to 1.11; p
=0.06 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.