Rabu, 07 Maret 2012

Does Drinking Coffee Increase Glaucoma Risk?

An analysis of the health records of more than 75,000 women has found a positive association between heavy coffee drinking and the development of exfoliation glaucoma (EG) or EG suspect, according to data presented here at the American Glaucoma Society 22nd Annual Meeting.

"We believe that coffee consumption is a reasonable candidate to consider," said lead investigator Louis Pasquale, MD, FARVO, associate professor of ophthalmology at Harvard Medical School in Boston, Massachusetts.

Dr. Pasquale explained that previous randomized trials have indicated that homocysteine levels, a risk factor for coronary disease, are increased after coffee consumption, and that patients with EG have elevated homocysteine in the aqueous humor and tears.

Dr. Pasquale and colleagues used data collected in the Nurses' Health Study from 1980 to 2008 for their study. To be included, subjects had to be at least 40 years of age, had to have no history of glaucoma or cancer, and had to have reported eye exams.

Patients were identified as having EG if there was evidence on a slit-lamp exam and 2 or more reliable visual fields showing reproducible loss. For patients with EG suspect, the presence of exfoliation material on the slit-lamp exam was required, as was an intraocular pressure (IOP) above 21 mm Hg or a cup-to-disc ratio of 0.6 or higher.

A validated questionnaire was used to assess total caffeine intake (from coffee, tea, soda, and caffeine-containing food) every 4 years. A multivariate analysis was performed to determine the association between caffeine consumption and the incidence of EG.

The investigators found 300 cases of EG over 1.6 million person-years of follow-up.
Women who consumed 500 mg caffeine or more per day (1 cup of coffee has roughly 150 mg of caffeine) had a nonsignificant but numerically increased risk for EG (P = .06), compared with those who consumed less than 125 mg per day.

People who drank 3 or more cups of coffee daily had a relative risk (RR) for EG of 1.63 (95% confidence interval [CI], 1.03 to 2.57; P = .02), compared with those who abstained from drinking coffee.

The association between coffee intake and EG was stronger in people with a family history of glaucoma (RR, 2.9; CI, 1.16 to 7.47) than in people with no family history (RR, 1.16; CI, 0.27 to 1.88).

"This strongly suggests that there is a gene interaction with the environment at play here," Dr. Pasquale said.
Given these data, which he cautions are preliminary, Dr. Pasquale does not think that routine checking of homocysteine levels or advising changes in coffee consumption are warranted until stronger associations are proven.

Moderation in All Things
A second study reported here at the American Glaucoma Society meeting was an investigation of the effect of modest caffeine intake — one 8 oz (237 mL) cup of coffee — on IOP.

"Studies in the past have shown conflicting evidence about IOP and caffeinated coffee," explained Aliya Jiwani, BA, from the Massachusetts Eye and Ear Infirmary in Boston. "To date, there are no double-blind randomized controlled trials that examine the effect of coffee on IOP, ocular perfusion pressure [OPP], or ocular pulse amplitude [OPA] in those who have glaucoma or those at risk. This is the first trial of its kind."

This prospective investigation involved 106 subjects — 22 with high-tension primary open-angle glaucoma (POAG), 18 with normal-tension POAG, 20 with ocular hypertension, 21 with suspected POAG, and 25 healthy control subjects.

Randomized subjects ingested 8 oz of either caffeinated (182 mg) or decaffeinated (4 mg) coffee at the first clinic visit; at the second clinic visit, they ingested the alternate beverage. Blood pressure, IOP, OPA, and heart rate were measured before and 60 and 90 minutes after coffee consumption. The investigators calculated OPP (from blood pressure) and IOP.

At baseline, there were no differences in IOP, OPP, or OPA between treatment groups. Sixty minutes after caffeinated coffee intake, mean change in IOP was 0.99 mm Hg (P < .001), in OPP was 1.06 mm Hg (P < .001), and in OPA was 1.57 mm Hg (P = .013). Ninety minutes after caffeinated coffee intake, mean change from baseline in IOP was 1.26 mm Hg (P = .039), in OPP was 0.23 mm Hg (P < .001), and in OPA was 0.18 (P = .001).

Regression analysis revealed sporadic and inconsistent associations between caffeine intake and increases in IOP, OPP, and OPA.
"Although caffeine did have an observable effect in this cohort," Ms. Jiwani explained, "these 1-time modest increases are unlikely to have a clinical impact on this population."

American Glaucoma Society 22nd Annual Meeting: Abstracts 83 and 23. Presented March 3, 2012.

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