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Consuming caffeinated beverages such as tea and coffee is a common practice in many cultures around the world. While tea and coffee contain beneficial plant compounds such as antioxidants that lower the risk of disease, the caffeine in tea and coffee increases blood pressure, which may contribute to hypertension-related diseases such as chronic kidney disease, stroke, and glaucoma. Findings of a recent report detail the relationship between caffeine consumption and glaucoma risk.

In glaucoma, the pressure of fluid inside the eye (called intraocular pressure) increases, damaging the optic nerve at the back of the eye. Over time, as damage to the optic nerve accumulates, the risk of vision loss increases. While previous research investigating acute caffeine intake has demonstrated an increase in intraocular pressure following caffeine conumption, research on chronic caffeine consumption has found no relationship between caffeine intake and glaucoma risk. The risk of habitual caffeine consumption may depend on genetics, as other research has found a positive relationship between habitual caffeine intake and glaucoma in those with genetic susceptibility.

The authors conducted a genome-wide association study, a type of study in which researchers look for associations between gene variations called single-nucleotide polymorphisms and disease prevalence. The authors collected genetic data, clinical data measuring intraocular eye pressure, and self-reported dietary data regarding coffee and tea consumption from more than 100,000 participants enrolled in the United Kingdom Biobank study. Next, the authors calculated each participant’s polygenic risk score, which estimates an individual’s genetic susceptibility to a specific disease. Finally, the authors performed a Mendelian randomization analysis, which measures variation in specific genes in order to examine the cause and effect relationship between environmental factors (coffee consumption and total caffeine intake) and disease (glaucoma) risk.

The data revealed that greater total caffeine intake was associated with lower intraocular pressure, but the relationship was not statistically significant. Participants consuming the most caffeine (232 milligrams of caffeine per day or more, the amount in 20 ounces of coffee) had a reduction in intraocular pressure of 0.10 millimeters of mercury (the unit used for blood and eye pressure) compared to participants with the lowest caffeine intake (less than 87 milligrams per day, the amount in one 8-ounce cup of coffee).

Among participants with a high polygenic risk score for glaucoma, however, consuming greater amounts of caffeine (more than 480 milligrams per day, the amount in 42 ounces of coffee) was significantly associated with an increase in intraocular pressure of 0.35 millimeters of mercury compared to participants consuming the least caffeine (less than 80 milligrams per day, the amount in 7 ounces of coffee). While the authors found no overall relationship between caffeine intake and glaucoma, participants with high polygenic risk scores consuming 321 milligrams of caffeine per day or more were four times more likely to develop glaucoma.

The authors concluded that they found no relationship between caffeine consumption and glaucoma risk in the general population. However, their analyses revealed a significant relationship between higher caffeine consumption and increased risk of high intraocular pressure and glaucoma incidence in those with the highest genetic susceptibility for the disease.

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