Coffee, Caffeine and Glaucoma, What's the Connection?
Could your morning cup of java increase your chance of going blind? Results of a new study suggest that people who drink coffee that contains caffeine have an increased risk of developing glaucoma, a progressive eye disease that leads to vision loss.
Should you drink tea instead of coffee?
Glaucoma is a term for a group of eye disorders that involve damage to the optic nerve, which can result in vision loss or complete blindness. According to National Glaucoma Research, more than 3 million Americans have glaucoma, while the worldwide estimate is 60.5 million, with an increase to nearly 80 million by 2020.
Glaucoma appears in two main forms: primary open-angle, which affects about 95 percent of people who develop the disease; and angle closure, also known as acute glaucoma. Variants of open-angle and angle closure glaucomas include secondary glaucoma, pseudoexfoliative glaucoma, traumatic glaucoma, neovascular, and pigmentary glaucoma.
The new study was conducted by experts at Brigham and Women's Hospital under the leadership of Jae Hee Kang, ScD. It is the first study of its kind done with a US population and was undertaken because:
- Kang's team had previously discovered that greater intake of caffeinated coffee was associated with an increased risk of open-angle glaucoma
- Scandinavians, who consume the most caffeinated coffee in the world, also have the highest frequencies of glaucoma and exfoliation syndrome, which causes exfoliation glaucoma, the most common known cause of glaucoma. Exfoliation syndrome is a condition characterized by flaky white material that builds up in the eye.
- About 10 percent of individuals older than 50 exhibit signs of exfoliation syndrome, although Scandinavians have the highest known rates. People of Indian, Irish, Japanese, Middle Eastern, and Russian Jewish ancestry also have high rates of exfoliation syndrome. The risk of developing glaucoma among people with exfoliation syndrome is 5 to 10 times more common than in people without the syndrome.
In the new study, the researchers set out to determine if the risk of developing glaucoma or exfoliation glaucoma may be influenced by coffee consumption. Data from individuals 40 years or older who did not have glaucoma and who underwent eye examinations and who participated in the Nurses' Health Study (78,977 women) and the Health Professionals' Follow-up Study (41,202 men) were used.
Investigators considered survey information regarding beverage consumption and medical records regarding cases of exfoliation glaucoma. This is what they found:
- People who drank three or more cups of caffeinated coffee daily were at greater risk of developing glaucoma exfoliation or glaucoma suspect, which is an individual who has one or more risk factors that may result in glaucoma, including increasing intraocular pressure, but does not yet have definite optic nerve damage or loss of vision
- Women with a family history of glaucoma had an elevated risk of glaucoma exfoliation
- Researchers did not discover any association between consumption of decaffeinated coffee or with other products that contain caffeine, such as colas, tea, or chocolate
Previous studies of coffee and glaucoma
A study published in the August 2012 issue of Eye (London) explored the impact of drinking caffeinated coffee on intraocular pressure (IOP), ocular perfusion pressure (OPP), and ocular pulse amplitude (OPA)--all factors associated with primary open-angle glaucoma. The double-blind, randomized, crossover trial included 81 individuals with primary open-angle glaucoma or who were glaucoma suspects, and 25 healthy subjects.
All the participants consumed either 237 ml of caffeinated (182 mg caffeine) or decaffeinated (4 mg caffeine) coffee on the first session and the other beverage on the second. Overall, researchers found that drinking one cup of caffeinated coffee statistically increased, but probably did not have a clinical impact, on IOP and OPP in people with or at risk for primary open angle glaucoma.
A prior meta-analysis sought to identify the effect of caffeine on intraocular pressure in people with or without glaucoma or ocular hypertension. Six randomly controlled trials with a total of 144 participants were reviewed. The reviewers reported that caffeine did not change IOP in normal individuals but that it did significantly increase it in patients with glaucoma or ocular hypertension.
Prior to the latest study, no others had been done to evaluate the association between consuming caffeinated coffee and exfoliation glaucoma among a US population. Therefore, Kang noted that "confirmation of these results in other populations would be needed to lend more credence to the possibility that caffeinated coffee might be a modifiable risk factor for glaucoma."