Study: Low prevalence of late AMD found in Hispanic population

Prevalence of early AMD was higher than in whites. Reasons for the differences are unclear, researchers said.

Issue: February 1, 2006

ByMichelle Dalton

ByJared Schultz

Early age-related macular degeneration changes were common in a study in a U.S. Hispanic population, but the prevalence of late AMD in that population was lower than estimates for white people in the United States.

This finding from Proyecto VER (Vision and Eye Research), a population-based study of blindness and visual impairment in Hispanic people in Arizona, is published in Archives of Ophthalmology. Beatriz Muñoz, MSc, and colleagues investigated the prevalence of AMD in participants age 50 years and older in Proyecto VER.

“Although Hispanic people are the second largest minority in the United States, there are limited data available on the prevalence of AMD in this ethnic group,” the study authors said.

In the study, 2,780 patients had fundus photographs of sufficient quality to grade early and late AMD. Each participant was evaluated for signs including drusen size and type, pigment abnormalities, geographic atrophy and exudative AMD.

The overall prevalence of late AMD was 0.5%. The prevalence of late AMD increased with age; 0.1% of participants in the 50- to 59-year range had late AMD, increasing to 4.3% in those age 80 years and older.

Early AMD was also strongly associated with age. Twenty percent of patients in the 50- to 59-year range had early AMD, and the prevalence rose to 54% in those age 80 years and older.

“The prevalence of early AMD in Hispanic people was significantly higher than the reported prevalence in the white population,” the study authors said. “However, the prevalence of late AMD was lower than the estimates for the white population in the United States.”

Further studies are needed to evaluate the different patterns of presentation of AMD among ethnic groups, the authors said.

Possible explanations

The study authors offered hypotheses to attempt to explain the differences they found.

Medicare expands glaucoma screening coverage

The Centers for Medicare and Medicaid Services has released a final rule to expand Medicare coverage of glaucoma screening to Hispanic-Americans. The final rule extends glaucoma screening benefits to Hispanic-Americans age 65 or older because they are identified as an ethnic group at high risk of the disease, according to a CMS press release. This benefit was limited to individuals with diabetes, people with a family history of glaucoma and African-Americans age 50 or older. The rule was to become effective for services provided on or after Jan. 1, 2006, according to the release.

One possibility is that there is a lower survival rate in Hispanics with AMD; however, they said previous data on the relationship between mortality and AMD has not been consistent.

“If mortality is explaining the lower rates of severe AMD in Hispanic people, the differential mortality would have to be higher for Hispanic than for non-Hispanic white people,” they said. “In this cross-sectional study, we cannot exclude that possibility.”

Another possibility is that, for unknown reasons, Hispanic people do not progress to geographic atrophy or exudative AMD despite a high prevalence of early signs of AMD.

Past studies have suggested that choroidal and retinal pigment epithelium pigmentation are protective against progression to neovascular AMD, and that genetic differences may be an explanation, the researchers noted.

They also theorized that large drusen may progress to advanced AMD at a different rate in this population.

The size of drusen in the study increased with age. The prevalence of large drusen, defined as 125 µm or more in diameter, increased from 11% in the younger age group to almost 40% in the group age 80 years and older.

Drusen greater than 250 µm increased with age from 15% in the younger age group to 37% after age 80, they said.

“The question of whether large drusen are more likely to progress to advanced AMD in this population can only be addressed in longitudinal studies,” the authors said. “Such studies in different racial and ethnic groups are warranted to further characterize the natural history of AMD.”

Patient exclusions

According to the authors, 371 Proyecto VER participants were excluded from the late AMD prevalence calculations because fundus photographs were not available. They said those excluded were significantly older, more likely to have had cataract surgery, more likely to be visually impaired, more likely to report diabetes and less likely to have 12 or more years of education.

“The observed differences in frequency of AMD in Hispanic people and non-Hispanic white people are unlikely the result of differentially excluding from analysis the people more likely to be affected with late AMD in our study,” they said. “For the prevalence of late AMD in Hispanic people to reach the level of what has been estimated for white people, 40 out of the 371 nonparticipants … need to have had late AMD, which is a very unlikely scenario.”

A note from the editors:
Portions of this article originally appeared on OSNSuperSite.com on Nov. 23, 2005. Visit OSNSuperSite.com for daily ophthalmic news updates.

For Your Information:

Beatriz Muñoz, MSc, can be reached at the Wilmer Eye Institute, Room 118, Johns Hopkins University, 600 N. Wolfe St., Baltimore, MD 21287; 410-955-2556; fax: 410-955-0096; e-mail: bmunoz@jhmi.edu.

Reference:

Muñoz B, Klein R, et al. Prevalence of age-related macular degeneration in a population-based sample of hispanic people in Arizona: Proyecto VER. Arch Ophthalmol. 2005;123:1575-1580.

Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.

Michelle Dalton is Managing Editor of OSNSuperSite.com. She writes daily updates on developments in all aspects of ophthalmology.