By Lisa Collier Cool
A new Harvard study has discovered a high incidence of vision problems among men and women who drank three or more cups of coffee a day. The research, published in Investigative Ophthalmology & Visual Science, linked heavy consumption of caffeinated coffee with increased likelihood of developing exfoliation glaucoma, an eye disorder that affects about 10 percent of adults over age 50 and can lead to vision loss or blindness.
Specifically, the researchers reported that adults who drank three or more cups of coffee daily were 34 percent more likely to develop exfoliation glaucoma, compared to those who abstained from coffee. Women with a family history of glaucoma were at the highest risk, with their threat of exfoliation glaucoma soaring by 66 percent if they quaffed three or more cups of java per day.
Here’s a closer look at the study and what it means for coffee-lovers.
What is exfoliation glaucoma?
Glaucoma, the second leading cause of blindness in the world, affects 60 million people. It is a group of painless diseases that can damage the optic nerve, if untreated. Typically, this damage results from increased pressure within the eye, usually due to fluid buildup.
Think of the eye as a sink in which the faucet is always running and the drain is always open. A tiny gland behind the iris produces fluid to nourish the cornea and lens, then the fluid flows out of the eye through spongy tissue called the trabecular network, explains the Glaucoma Foundation.
Exfoliation glaucoma, sometimes called “exfoliation syndrome,” is marked by tiny, dandruff-like flakes building up on the lens of the eye. The flakes are rubbed off as the lens of the iris (colored part of the eye) moves, causing the spongy tissue that normally serves as the eye’s drain to get clogged. The result is increased pressure, sometimes very high pressure, inside the eye. The cause of exfoliation glaucoma is unknown, but genetics appear to play a role.
How was the study conducted?
The Harvard study was the first to link heavy coffee consumption and glaucoma risk in Americans by analyzing data from nearly 79,000 women in the well-known Nurses’ Health Study (NHS) and more than 42,000 men in the Health Professionals Followup Study (HPFS).
The researchers looked at men and women ages 40 or older who did not have glaucoma at the start of the study, and had received eye exams from 1980 (for women in the NHS) or 1986 (for men in the HPFS) to 2008. The study looked at health questionnaires the participants filled out about consumption of caffeinated drinks, including coffee, and their medical records (to identify cases of exfoliation glaucoma).
The analysis showed a significant rise in incidences of exfoliation glaucoma among people who drank three or more cups of coffee, but no link between drinking other caffeinated beverages, such as soda or tea.
The Scandinavian Link
"Scandinavian populations have the highest frequencies of exfoliation syndrome and glaucoma," author Jae Hee Kang, ScD, of Channing Division of Network Medicine at Brigham and Women's Hospital in Boston, told Science Daily.
"Because Scandinavian populations also have the highest consumption of caffeinated coffee in the world and our research group has previously found that greater caffeinated coffee intake was associated with increased risk of primary open-angle glaucoma [another form of the disease], we conducted this study to evaluate whether the risk of exfoliation glaucoma…may be different by coffee consumption,” Kang added.
Should you cut down on coffee?
As I’ve reported previously, coffee has a number of health perks, including reducing risk for superbug infections, diabetes, strokes, and breast and prostate cancer. Kang emphasizes that further study is necessary to find direct evidence that heavy consumption of caffeinated coffee is indeed a risk factor for exfoliation glaucoma.
“If [the findings are] confirmed,” she told HealthDay News, “those at risk of exfoliation glaucoma—particularly those with a family history of glaucoma—would be recommended to limit their intake [of coffee] to less than three cups per day.”
Several eye experts say that they’re not cutting down on java—at least not yet, because this type of study is not designed to prove a cause-and-effect relationship. Therefore, variables other than drinking large amounts of caffeinated coffee may explain the apparent association with glaucoma.
Who is at risk for glaucoma?
Because glaucoma is painless, many people don’t know they have it until irreversible vision impairment occurs. To detect it in the early, treatable stages, the Mayo Clinic recommends getting a comprehensive eye exam every three to five years starting at 40 and annually starting at 60.
Screening is particularly crucial if you have any of these risk factors, says the Glaucoma Foundation:
- Being over 60. You are six times more likely to develop glaucoma if you’re older than 60.
- Family history. Having close relatives with glaucoma multiples your risk by four to nine times.
- Steroid medication use. One study found that heavy use of inhaled steroids for asthma boosted glaucoma risk by 40 percent.
- Ethnicity. African-Americans are six to eight times more likely to develop glaucoma than Caucasians. People of Hispanic ancestry are also at higher risk.
- Eye injury. Blunt injuries that “bruise” the eye can lead to glaucoma, either soon after the injury or years later. Use protective eyewear for activities that may cause eye injury, such as sports like boxing or baseball, or using power tools.