NEW YORK (Reuters Health) - Overweight older women may be less likely than their thinner peers to develop the potentially blinding eye disease glaucoma, a study published Monday suggests.
Researchers found that of nearly 4,000 older Dutch adults followed for a decade, heavier women were less likely to be diagnosed with so-called open-angle glaucoma. There was no clear link, however, between weight and glaucoma risk among men.
Open-angle glaucoma is the most common form of glaucoma. It arises when fluid buildup increases pressure in the eye, damaging the optic nerve that runs from the eye to the brain.
The new findings, reported in the Archives of Ophthalmology, may sound counterintuitive, since obesity would seem likely to boost pressure in the eye. And, in fact, overweight and obese women in the study did have somewhat greater pressure within the eye -- called intraocular pressure.
But the researchers speculate that there may be something protective about extra fat tissue in women -- like increased estrogen levels -- that helps lower their risk of glaucoma.
Still, no one is suggesting that women pack on extra pounds as a way to ward off glaucoma.
The best way to prevent vision loss from the disorder is to have regular eye exams and, if glaucoma is found, early treatment, according to Dr. Johannes R. Vingerling, a professor at Erasmus Medical Center in Rotterdam, the Netherlands, and one of the researchers on the study.
"The best therapy is to lower eye pressure in these people," Vingerling told Reuters Health in an e-mail. That can be done with medicated eye drops or, in some cases, surgery.
Eye exams are particularly important for people at increased risk of glaucoma, Vingerling pointed out. That includes people older than 60, anyone with a family history of glaucoma, and in the U.S., African Americans and Mexican Americans.
For their study, Vingerling and his colleagues followed 3,939 initially glaucoma-free adults aged 55 or older. Over an average of 10 years, just under three percent developed open-angle glaucoma.
Among women, the study found, each unit increase in body mass index (BMI) -- a measure of weight in relation to height -- was connected to a seven percent reduction in the risk of developing glaucoma.
A "unit increase" in BMI is equal to a roughly six-pound gain for a woman of average height and weight.
There was no evidence that other lifestyle factors, including smoking and drinking habits, were important in participants' glaucoma risk. Nor did education or income appear to play a role.
The findings do not prove that extra pounds, themselves, are protective in women. But one possibility, Vingerling's team speculates, is that there is some benefit from the higher estrogen levels that may be found in women with more body fat.
The findings do back up a U.S. study published last August -- the first one to show a link between higher BMI and lower glaucoma risk in women.
But the reasons for the connection remain unclear, said Dr. Louis Pasquale, an associate professor of ophthalmology at Harvard Medical School who led the U.S. study.
"Until we can discover those mechanisms, no recommendation about an ideal body weight to prevent glaucoma can be made," Pasquale told Reuters Health in an e-mail.
An estimated four million Americans have glaucoma, but only half of them know it. African-Americans are at especially high risk. Open-angle glaucoma causes 19 percent of all cases of blindness in African Americans, for example, versus six percent of blindness in Caucasians.
Based on what's known about glaucoma, there is little people can do to curb their risk beyond getting regular eye exams.
Corticosteroid medications, whether topical, oral or inhaled, have been linked to an increased glaucoma risk. So if it's possible to minimize your exposure to those drugs, it would help lower the odds of developing glaucoma, Pasquale noted.
To help catch glaucoma early, the American Academy of Ophthalmology recommends that all adults start having comprehensive eye exams at the age of 40. People at increased risk of glaucoma may be advised to start those exams earlier, or have them more frequently.
SOURCE: bit.ly/dwLuPs Archives of Opthalmology, online February 14, 2011.