Denser bones tied to healthier eyes in aging women

NEW YORK (Reuters Health) - The denser an older woman's bones, the lower her risk of a sight-threatening condition known as age-related maculopathy (ARM), a new study shows.

While it's not clear how bone mineral density (BMD) and ARM are connected, it's possible BMD may signal greater lifelong exposure to estrogen, which has been suggested to help guard against ARM, note Dr. Robin Seitzman of the David Geffen School of Medicine in Los Angeles and colleagues.

ARM is the most common cause of vision loss among people age 65 and older in the developed world. The causes of ARM aren't clear, although some researchers have proposed that in women, exposure to estrogen and progestin could be a factor; one study found women on hormone therapy had a lower risk of developing ARM.

Given that BMD can serve as a marker for the amount of estrogen a woman has been exposed to throughout her life, with greater exposure tied to denser bones, the Seitzman's team investigated BMD and ARM in 1,042 women participating in a long-term study of osteoporosis risk.

Half of the women had ARM, with 46 percent in the early stage of the disease and 4 percent with late-stage ARM, the researchers report in the Journal of the American Geriatrics Society.

The one-fourth of women with the greatest BMD were at 34 percent lower risk of having ARM than all of the women with lower BMD, and were 37 percent less likely to have ARM than the one-quarter of women with the lowest BMD.

"BMD may serve as a marker for lifetime endogenous estrogen exposure, and if so, these results suggest that endogenous estrogen exposure may be protective against ARM," the researchers write. Nevertheless, other factors that affect BMD, such as calcium and vitamin D intake, fruit and vegetable consumption, or osteoporosis-preventing drugs could also play a role in the relationship, they point out.

More research is needed to clarify the link between BMD and ARM, the researchers conclude.

SOURCE: Journal of the American Geriatrics Society, May 2007