Incidence and progression of AMD in Latinos
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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.
Am J Ophthalmol. 2010 May;149(5):741-51
http://www.ncbi.nlm.nih.gov/pubmed/20399926
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