Incidence and progression of AMD in Latinos The 4-year incidence and progression of age-related macular degeneration (AMD) in Latinos are lower than in non-Hispanic whites, according to a report from the Latino Eye Study.

Latinos represent the largest of minority populations in the United States. According to the 2004 US Census, 35.6 million people, or 12.5% of the nation's residents, are Latino. This proportion is expected to increase to 20.1% by the year 2030. The Latino population has unique demographic, socioeconomic, and ocular health characteristics that influence the development of eye disease and its subsequent impact on quality of life.

Various population-based longitudinal studies of eye disease have been conducted on non-Hispanic whites, including the Beaver Dam Eye Study in Wisconsin and the Blue Mountains Eye Study in Australia. Other studies such as the Barbados Incidence Study of Eye Disease have focused on a population of African origin. Although these studies reported data on the incidence and progression of age-related macular degeneration (AMD), given the wide variation in the prevalence and incidence of AMD it would be inaccurate to generalize findings from these studies to people of other ancestries. As observed in cross-sectional studies, there were differences in the prevalence of both early and advanced AMD between non-Hispanic whites and Latinos. Findings from the baseline Los Angeles Latino Eye Study (LALES) reported that age-specific prevalence of early AMD was lower in Latinos (who have 40% European ancestry and 45% Native American ancestry) than the non-Hispanic whites of Beaver Dam, Wisconsin but higher than those from Blue Mountains, Australia. On the other hand, age-specific prevalence of advanced AMD was marginally lower in Latinos compared to the non-Hispanic white populations of both studies. Most interestingly, the prevalence of large drusen, a well-recognized predictor of incident advanced AMD in non-Hispanic whites, was considerably higher in Latinos than in whites. Thus, it is of considerable interest to determine if the incidence and progression of early and advanced AMD in Latinos is comparable to those of non-Hispanic whites.

Methods & Results

The Los Angeles Latino Eye Study is a population-based cohort study of eye disease in self-identified Latinos aged 40 years and older living in 6 census tracts in the city of La Puente, Los Angeles County, California. Latinos (Hispanics, Hispanic Americans, and Latino Americans) are individuals who are born into or have descended from a Spanish-speaking community, regardless of race. In the United States they are a heterogeneous group, with the majority of Mexican ancestry (66%). Baseline examination was performed from 2000 to 2003 with 4-year follow-up examination from 2004 to 2008.

A comprehensive ophthalmologic examination including stereoscopic fundus photography was performed on adult Latinos at baseline and follow-up. Photographs were graded using a modified Wisconsin Age-Related Maculopathy Grading System. For estimations of incidence and progression of AMD, the Age Related Eye Disease Study Scale was used. Main outcome measures are incidence and progression of early AMD (drusen type, drusen size, and retinal pigmentary abnormalities) and advanced AMD (exudative AMD and geographic atrophy).

A total of 4658 of 6100 subjects (76%) completed the follow-up examination. The 4-year incidence of early AMD was 7.5% (95% CI: 6.7, 8.4) and advanced AMD was 0.2% (95% CI: 0.1, 0.4). Progression of any AMD occurred in 9.2% (95% CI: 8.3, 10.1) of at-risk participants. Incidence and progression increased with age. Incidence of early AMD in the second eye (11.2%) was higher than incidence in the first eye (6.9%). Baseline presence of soft indistinct large drusen >or=250 microm in diameter was more likely to predict the 4-year incidence of pigmentary abnormalities, geographic atrophy, and exudative AMD than smaller or hard or soft distinct drusen.

Discussion & Conclusions

The Los Angeles Latino Eye Study (LALES) is the first longitudinal study to provide data on the incidence and progression of AMD and its associated lesions in a large, well-defined cohort of adult Latinos. The use of standardized protocols at both baseline and follow-up, particularly the identical grading procedure carried out by the same graders, ensured data compatibility between the 2 time points.

The LALES also used the AREDS classification scheme in describing AMD incidence and progression. This scheme defines risk categories and grades for the severity of AMD characteristics along an ordinal scale. Using this scale, AMD progression of 2 or more steps was found in 9% of subjects over 4 years in our population. Using this severity scale, we found that 7.5% and 0.2% of the overall LALES population had a 4-year incidence of early and advanced AMD, respectively.

The use of near-identical methods and photography grading procedures between the LALES, the Beaver Dam Eye Study (BDES), and the Blue Mountains Eye Study (BMES) allows for general comparison of data across populations, although the numbers of incidence cases in LALES was low. Annualized results show that the incidence of early AMD in Latinos was lower than observed in non-Hispanic whites of the other 2 studies (annual incidence, 0.8% in LALES, 1.6% in BDES, 1.5% in BMES) (see TABLE). A similar trend was also observed for the incidence of advanced AMD (annual incidence, 0.05% in LALES, 0.18% in BDES, 0.16% in BMES). Given that the LALES study cohort was generally younger than the BDES and BMES populations, we stratified the annual incidence rates by age groups consistent with the 2 studies, and removed from our analysis 18 people aged 40 to 42 at risk for early AMD and another 192 people of the same age range at risk for advanced AMD. We found that the annual incidences for both early and advanced AMD at each of the age strata remained lower in LALES than in BDES or BMES. We also age standardized the overall rates of the 3 studies to the LALES population. The age-standardized rates for early AMD were 0.95, 1.73, and 1.41 for LALES, BDES, and BMES, respectively, still consistent with the unadjusted rates. Similarly, the rates for late AMD were suggestive of a lower trend for LALES (age-standardized rates: LALES 0.11, BDES 0.18, BMES 0.15). This suggests possible variations in AMD disease development along the different ethnicities. Further examination of known genetic and environmental risk factors may explain these differences. For example, the homozygous CFH Tyr402His polymorphism is present in only 3% of our LALES population compared to 9% to 21% of non-Hispanic whites.

Comparisons with other population-based studies are difficult because different methodologies were employed for the assessment of AMD. Descriptively, the Barbados Eye Studies reported a 4-year incidence of 5.2% for early AMD in their predominantly Afro-Caribbean population, which appeared to be lower than the rate found in our Latino population. This parallels the prevalence data of both studies where early as well as advanced AMD were less prevalent in the Barbados cohort than in LALES. Elsewhere, the Melbourne Visual Impairment Project reported a 5-year incidence of 5.4% for early AMD when definitions were standardized to those used in BMES. Two other studies in Europe also provided estimates of AMD incidence and progression in non-Hispanic white populations. In the Copenhagen City Eye Study, Buch and associates found similar incidence rates of early ARM (age-related maculopathy) when compared to BDES (a US study), and slightly higher rate of late AMD possibly attributable to their older population (60–80 years of age), whereas in the Rotterdam Study, Klaver and associates found similar incidence estimates of late AMD, but not early ARM, when compared to BDES, possibly attributable to the short follow-up duration.

In this LALES study we have detailed the interrelation of AMD lesions over time. Soft indistinct drusen and large drusen (≥250 µm) stood out as the strongest predictors of incident pigmentary abnormalities. Other studies have previously shown that this type and size of drusen increases the risk of advanced AMD. However, we cannot conclude that this is the case for the Latino population because of the low incidence of advanced AMD in the current 4-year cohort.

When documenting the incidence of eye disease, it would be useful to quantify occurrence in the subject's first eye as well as second eye, which we have done in this report. The respective incidence estimates would refer to 2 separate at-risk cohorts of participants, where the former was free of disease in both eyes at baseline while the latter had previously reported presence of unilateral disease. In the case of AMD, a study by Gudnadottir and associates reported that 82% of individuals with unilateral exudative AMD developed the same condition in the second eye within 4 years, resulting in bilateral advanced AMD. People with bilateral severe AMD had reported significantly lower vision-related quality of life than those with AMD of varying severity.

In conclusion, age-specific incidence and progression of AMD in Latinos are lower than in non-Hispanic whites. While incident early AMD is more often unilateral, the risk of its development in the second is higher than in the first eye. Older people and those with soft indistinct large drusen had a higher risk of developing advanced AMD compared to those who were younger and did not have soft indistinct large drusen. While these data show low incidence and progression of AMD in the Latino population, it is not yet understood whether this is attributable to protective genetic and lifestyle factors relative to whites.

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Am J Ophthalmol. 2010 May;149(5):741-51