Purpose:
To investigate the relationship between glaucoma and the supplementary consumption of the oxidants calcium and iron.
Methods:
This cross-sectional study included 3848 participants in the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2008, age≥ 40 years, who reported a presence or absence of glaucoma. Participants were interviewed regarding use of prescription and non-prescription dietary supplements and antacids during the prior 30-day period. Supplementary intake of calcium and iron was aggregated across all reported dietary supplements and antacids, and intake was divided into quintiles. Information on the main outcome, a diagnosis of glaucoma, as well as demographics, comorbidities, and health-related behaviors was obtained via interview.
Results:
Participants who consumed ≥800mg/day of supplementary calcium or ≥18 mg/day of supplementary iron had significantly higher odds of self-reported glaucoma compared to no consumption of supplementary calcium or iron, after adjustment for demographic characteristics, health-related behaviors, comorbidities, and general health condition (OR 2.44, 95% CI 1.25-4.76 for calcium; OR 3.80, 95% CI 1.79-8.06 for iron). These nutrient intake levels were equivalent to the highest quintile of calcium intake and the highest two quintiles of iron intake in this population. Concurrent consumption of supplementary calcium and iron above ≥800 mg/day of calcium and ≥18 mg/day of iron was associated with still greater odds of glaucoma (OR 7.24, 95% CI 2.42-21.62). We did not find a dose-response relationship between quintiles of supplementary calcium or iron intake and glaucoma.
Conclusions:
Since we found that only those with the highest quintiles of supplementary calcium and iron consumption had significantly greater odds of glaucoma, we postulate that there may be a threshold intake of these oxidants above which there is an increased risk of glaucoma. Further research is needed to elucidate the potential mechanisms by which consumption of the calcium and iron may be related to neurodegeneration and glaucoma, and to determine whether calcium and iron intake may increase the risk of glaucoma progression.
Keywords: nutritional factors • clinical (human) or epidemiologic studies: risk factor assessment • calcium