13
Epidemiology of AMD
1
Although age-related macular degeneration (AMD) is
the third cause of blindness worldwide, and the first in
industrialized countries
(1)
, epidemiological data on this
disease remain scarce and partial. The very first studies
were published in the 1980’s. Since then, a number of
population-based studies have been conducted, first in
Caucasian populations of the United States and other
industrialized countries (Australia, Europe). Studies have
more recently been extended to other ethnical subgroups
of industrialized countries (African Americans, Latinos)
and to other parts of the world (India, China, and Japan).
2. Prevalence of late AMD in Caucasians
from industrialized countries
The prevalence of late AMD in the main epidemiological
studies performed in Caucasians of industrialized coun-
tries are presented in Table 1. The included studies were
restricted to those having classified AMD from retinal
photographs and used the international classification
(2)
,
in order to make comparisons between studies easier.
In these studies, late AMD is defined by the presence
of neovascular AMD and/or geographic atrophy. In the
United States, the prevalence of late AMD ranged from
0.2% to 1.6% according to studies. Since the preva-
lence of late AMD increases sharply with age, most of
the differences between studies were due to differences
in the age distribution. For instance, the lowest preva-
lence rate (0.2%) was observed for the Atherosclerosis
Risk in Communities (ARIC) Study. In this study, the
age range of participants was 48-72 years, thus excluding
the oldest subjects, in which the prevalence of late AMD
is the highest. This study also performed photographs in
only one eye of each participant, which may have led to
undetected unilateral cases and thus underestimation of
the prevalence of late AMD. This is also the case for the
Cardiovascular Health Study, which also found relatively
low prevalence (1.3% in subjects aged 69 to 97 years).
Prevalence rates observed in Caucasians from Australia
and Europe appear relatively similar to those observed
in the United States (Table 1), when taking into account
differing age distributions in the different studies. In
European studies, the prevalence of late AMD ranged
from 1.65% to 3.5%.
In order to better compare the prevalence rates among
studies, age-specific prevalence rates need to be estimated.
This has been done in a meta-analysis performed in 2004
by Friedman et al
(3)
. The authors concluded that preva-
lence rates were not different among Caucasian popula-
tions of industrialized countries, including the United
States, Australia and the Netherlands. Similarly, in the
EUREYE Study, which included 7 European countries
(Norway, Estonia, Ireland, France, Italy, Greece, Spain),
no significant differences were found among the partici-
pating countries
(4)
.
Therefore, the prevalence of late AMD appears to be
similar in the Caucasian populations from the United
States, Australia and European countries, despite
major geographical and lifestyle differences. Thus, the
meta-analysis from Friedman et al. probably constitutes
the most reliable available estimate of prevalence rates for
these countries, since it bears on studies gathering alto-
gether more than 25000 subjects
(3)
. In this meta-analysis,
the prevalence rates increase sharply with age (Fig. 1),
from less than 0.5% in subjects 50 to 60 years, to 12%
and 16% in men and women aged 80 years or more,
respectively. While men tend to have higher prevalence
rates than women in the younger age groups (less than
80 years), late AMD is more frequent in women than
in men in the oldest age group (80 years or more). This
may be due to the higher mortality in ageing men, which
leads to a higher selection of the oldest subjects.
1. Introduction
Author:
Cécile Delcourt, MD, PhD
Inserm, U897, Bordeaux, France
Université Bordeaux 2, Bordeaux, France
