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A. G. Tan, P. Mitchell, E. Rochtchina, V. M. Flood, R. G. Cumming, J. J. Wang, Blue Mountains Eye Study; Serum Homocysteine, Vitamin B12, Folate and the Prevalence of Age-Related Cataract. Invest. Ophthalmol. Vis. Sci. 2009;50(13):510.
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It has been hypothesized that homocysteine may be a lens epithelilal stressor, via its contribution to the development of unfolded protein aggregates in the lens. We aimed to assess the associations between age-related cataract and serum levels of homocysteine, vitamin B12 and folate in an older population.
The Blue Mountains Eye Study (BMES) examined 3509 participants aged 49+ years at its second survey (1997-2000); 2335 (75.1% of survivors) were baseline study participants and 1174 (85.2% of those eligible) were newly recruited. Eye examinations included lens photographs (graded using the Wisconsin Cataract Grading System) and fasting blood tests. Nuclear cataract was defined as nuclear opacity >standard photo #3; cortical cataract was defined as any opacity involving ≥5% of the total lens area and posterior subcapsular (PSC) cataract as any PSC. Logistic regression models estimated odds ratios (OR) and 95% confidence intervals (CI) after adjusting for age and gender.
Higher levels of serum homocysteine were associated with greater prevalence of nuclear and PSC cataract (nuclear: OR 1.12, 95% CI 1.0-1.25, and PSC: OR 1.22, 95% CI 1.06-1.40, for each SD increase in serum homocysteine). In stratified analyses by age, these associations were marginally significant or significant only in younger baseline ages (<75 years); (nuclear: OR 1.14, 95% CI 0.99-1.31 and PSC: OR 1.24, 95% CI 1.05-1.47, per SD). We further excluded participants with low serum B12 levels (as low B12 elevates homocysteine), and the nuclear and PSC cataract associations with homocysteine persisted. Conversely, decreasing serum vitamin B12 level was associated with increased prevalence of cortical cataract (OR 1.11, 95% CI 1.01-1.22, for each SD decrease in serum vitamin B12). This association was significant in the older age (75+ years) group only (OR 1.21, 95% CI 1.04-1.42) in subgroup analysis. Folate levels were not associated with the prevalence of any cataract type.
This study reports that elevated serum homocysteine is associated with the presence of both nuclear and PSC cataract, and that reduced serum vitamin B12 was associated with the presence of cortical cataract. Some inconsistencies in these associations by age group were found, and the underlying pathogenesis of these links is unclear.
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