I know, no one wants to hear this -- especially the day after we went around the world in coffee shops -- but a 120,000-person study has tied drinking three cups per day to developing exfoliation glaucoma.
PROBLEM: A group at Harvard School of Public Health -- who'd previously conducted a smaller study that associated caffeine with a somewhat increased risk of primary glaucoma -- noted that people in Scandinavian countries have the highest rates of exfoliation glaucoma (EG) in the world, and that they also consume the most coffee. In an ongoing search for causes of EG, they suspected the two might be related. That was corroborated by knowledge that caffeine affects levels of homocysteine in our eyes, and that homocysteine levels are often high in people with EG.
A little on EG: The study's authors note it's "the leading cause of secondary open-angle glaucoma worldwide." It accounts for 7-12 percent of glaucoma. As we understand it, EG is due to pigments in your eye coming loose and blocking the flow of liquid out of your eyeball, which leads to increased pressure, changes in the optic nerve, and/or vision problems. A diagnosis of EG doesn't mean vision loss, though.
Lots of research on the causes of EG is happening. The stated purpose of this study was to look at risk factors for developing it.
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METHODOLOGY: Based out of Brigham and Women's Hospital in Boston, the researchers followed 78,977 women and 41,202 men, all initially without glaucoma who'd had eye examinations from the 1980s until 2008. They asked them all about their coffee (and other caffeine) habits, then compared them to their medical records if they reported a history of glaucoma, looking specifically for diagnoses of exfoliation glaucoma. They also counted diagnoses of "exfoliative glaucoma suspect." That included patients who had high pressures in their eyes, changes in their optic nerve, and/or visual field problems. They pooled the data from the cohorts via meta-analysis.
Note that they only measured regular coffee, not decaffeinated.
RESULTS: People who drank three or more cups of coffee every day were significantly more likely to have exfoliation glaucoma.
They didn't report on an association with actual vision loss.
The trend "did not robustly extend to caffeinated product consumption generally."
CONCLUSION: Drinking a lot of coffee is associated with increased risk of developing exfoliation glaucoma, and thereby a risk of impaired vision and blindness.
IMPLICATION: This is a large, prospective study worth factoring into the increasingly expansive discussion on coffee's plusses and minuses. "Life without life's joys is living death." And then, buried in the paper was this little gem: "The highest caffeine consumers were somewhat less likely to have hypertension, diabetes, high cholesterol, and myocardial infarction."
Takeaway, get screened for glaucoma regularly, even if you've never had any coffee ever. There were 44.8 million people with open-angle glaucoma in the world in 2010, and by 2020 there will be 58.6 million. We can't jump to saying this glaucoma-coffee association is definitely causal and that no one should drink coffee. I'm actually drinking some very bad coffee right now. If, for the time, though, these findings promote glaucoma awareness and continued research on the tremendous amounts of coffee and caffeine we drink/eat/rub all over our bodies, it's useful and good.
The study, "The Relation between Caffeine and Coffee Consumption and Exfoliation Glaucoma or Glaucoma Suspect," is published in the journal Investigative Ophthalmology and Visual Science.