Researchers in California found that study participants who drank one or more cups of caffeinated hot tea every day had 74% lower odds of developing glaucoma compared to those who consumed coffee, soft drinks and iced tea.
Dr. Anne Coleman of the University of California, Los Angeles, said, "Glaucoma can lead to blindness, and it would be great if it could be prevented because there is no cure." She told Reuters, "the best way to prevent it is to get your eyes checked. But we are also interested in lifestyle habits and what we can do to make a difference".
Glaucoma is the second leading cause of blindness globally, according to the World Health Organization. The condition affects an estimated 58 million people, including over three million Americans, only half of whom know that they have glaucoma, according to the Glaucoma Research Foundation.
Caffeine in general had been previously linked to a heightened risk for glaucoma, though recent studies disagree, Coleman and her research team said in their paper.
To assess the relationship between caffeinated drinks and glaucoma, Coleman and colleagues examined data on over 10,000 people in the United States who represented a sample of the population.
Participants in the National Health and Nutrition Examination Survey in 2005-2006 answered a survey on their diets and lifestyles, underwent medical exams and blood tests, and also had eye examinations.
Some 1,700 of the participants were older than 40 and had no known eye diseases. In that group, just over 5% of them had glaucoma.
Close to 50% of the participants said they drank coffee often, but less than 10% drank hot tea daily. The researchers did not find any links between coffee, iced tea, soft drinks or decaffeinated tea and an increase in glaucoma risk.
Coleman said, "Tea drinkers should keep drinking and don't need to stop because of a fear of glaucoma. This makes sense, but we'll see if it holds up in future studies."
The study was published in the British Journal of Ophthalmology.
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