Those who regularly drink coffee are likely to have lower intraocular pressure in their eyes compared to those who do not regularly drink coffee, according a study led by Kyoto University researchers.
The data was gathered from more than 9,000 participants, and the results countered a conventional theory that caffeine in coffee can cause an increase in pressure, which could lead to glaucoma. Based on this theory, many glaucoma patients tended to avoid drinking coffee, as increased intraocular pressure is one of the major causes of glaucoma.
Those with glaucoma suffer from partial vision loss, poor eyesight or can even become blind because of intraocular pressure and other variables that can damage the optic nerve. It is said that one in 20 people aged 40 and older have the disease in Japan. Many people that have a normal amount of intraocular pressure have also developed symptoms.
Masahiro Miyake, an ophthalmology specialist and a program-specific assistant professor at Kyoto University, and other members of the research team had analyzed data from a period of more than 10 years, looking at the relationship between health and lifestyle of Nagahama, Shiga Prefecture, residents.
The team focused on how frequently a person drank coffee and its effect on intraocular pressure. A group of 9,418 men and women in their 30s to 80s, who had never been diagnosed with glaucoma, were divided into four groups depending on their daily coffee intake ranging from "less than once a day" to "more than or equal to three times a day."
After adjusting for age, gender and other variables, the researchers calculated the average intraocular pressure (in mmHg) for each group. The results suggest the more frequently a person drank coffee, the lower their intraocular pressure tended to be. Those who drank coffee three or more times per day had intraocular pressure that was 0.4 mmHg lower compared to those who drank coffee less than once per day. The average value is 14.7 mmHg, and the normal range is 10 mmHg to 21 mmHg.
"Patients should consult their doctors [about drinking coffee], but it seems that glaucoma patients don't have to refrain from drinking coffee," Miyake said.
Miyake also said that because the current research did not look into whether coffee has any effect in lowering intraocular pressure, it is not recommended to drink it to prevent or treat glaucoma.
"Research studying the correlation between lifestyle and developing glaucoma is gaining momentum around the world," said Prof. Toru Nakazawa, an ophthalmology specialist at Tohoku University. "The results might be helpful to those patients who are concerned about what foods and drinks can affect their symptoms."
The research has been published in an online version of a U.S. medical journal on Nov. 6.
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