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Too much caffeine may raise risk of blinding eye diseases for some people, study finds

It depends on your genes.
Cup of coffee
(Getty Images)

Caffeine can do a lot more than give you shaky hands and a short-lived boost of energy; it can cause long-term health consequences if consumed in high enough amounts.

Now, a new study on more than 120,000 people found that drinking large amounts of caffeine can increase your risks of developing glaucoma specifically for people with certain genes that make them more likely to have high eye pressure — a risk factor for the group of diseases that can cause vision loss and blindness.

People who have the highest genetic risks for “intraocular” pressure and who reported consuming about three cups of coffee a day had a nearly four-fold higher prevalence of glaucoma compared to those with low genetic risks who drink minimal to no caffeine, according to the study published in the June print issue of the journal Ophthalmology.

On the plus side, the researchers didn’t find a connection between high caffeine intake and increased risk for high eye pressure or glaucoma among people without genetic predispositions. The team says its study is the “first to demonstrate a dietary-genetic interaction in glaucoma.”

The findings could help scientists and doctors “learn more than ever before about how our genes affect our glaucoma risk and the role that our behaviors and environment could play,” which has been largely understudied until now, study co-author Dr. Anthony Khawaja, an ophthalmic surgeon and an associate professor of ophthalmology at the University College London, said in a statement.

“Glaucoma patients often ask if they can help to protect their sight through lifestyle changes. This study suggested that those with the highest genetic risk for glaucoma may benefit from moderating their caffeine intake,” Khawaja said.

However, “it should be noted that the link between caffeine and glaucoma risk was only seen with a large amount of caffeine and in those with the highest genetic risk.”

The team of researchers from several institutions analyzed health records, as well as DNA samples, of more than 120,000 people between 2006 and 2010 who were between 39 and 73 years old and logged into the UK Biobank, a large-scale biomedical database.

Participants answered questions about their vision and family history of glaucoma, as well as on their daily diet, including how much caffeine they drink, the specific types of caffeine and the portion size. Three years into the study, researchers completed examinations of their eyes.

Among people within the top 25th percentile for genetic risks for high eye pressure, high caffeine consumption was associated with higher eye pressure and higher prevalence of glaucoma. And for those who drank about three cups of coffee a day, the risk for developing glaucoma was nearly four-fold compared to those with low genetic risks and low caffeine intake.

Genes and glaucoma

Glaucoma is one of the leading causes of blindness and vision loss for people over 60 and it typically happens when an eye’s optic nerve is damaged, according to the Mayo Clinic. Doctors aren’t entirely sure why this damage occurs, but it’s “usually related to increased pressure in the eye.”

And genes play a large role in determining who ends up developing it.

Over 60% of cases of infant blindness are caused by inherited eye diseases, the Cleveland Clinic says. Genes are also to blame for many vision problems such as lazy eye, nearsightedness, farsightedness and astigmatism.

People typically experience few or no symptoms until glaucoma progresses to vision loss, but those who are older, have poor vision, have had eye injuries, regularly take corticosteroid medications or those who are Black, Asian or Hispanic may face higher risks for the disease.

Experts say regular eye exams, exercise and eye protection are steps people can take to catch glaucoma early on and prevent or slow vision loss.