AMD in Japan
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MyVisionTest
Nov 25, 2009, 1:11:51 PM11/25/09
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The incidence of late age-related macular degeneration (AMD) among
the Japanese is lower than among white people in Western countries,
and is higher than among black people, according to a new study.
The pathogenesis of AMD remains poorly understood. It is thus very
important to determine the precise incidence of AMD and to identify
its risk factors to develop preventive measures of the disease. To
date, several population-based studies, have provided valuable
information on incidence and risk factors for AMD. The risk factors
examined include iris color, hypertension, atherosclerosis, smoking
habits, higher total/high-density lipoprotein ratio, and higher white
blood cell (WBC) count. However, information on the long-term risk of
AMD is scarce and nonexistent in Asians, including Japanese.
Methods and Results
In 1998, a total of 1775 residents of Hisayama, Japan aged ≥40 years
underwent a baseline eye examination. Of those, 1401 subjects (78.9%)
took part in the follow-up eye examination in 2007 and were enrolled
in the present study.
At both time points, the characteristics of AMD were determined by
grading color fundus photographs using the Wisconsin Age-Related
Maculopathy Grading System.
The age-standardized, 9-year cumulative incidence of early AMD was
10.0%, and that of late AMD was 1.4%. Men were found to have a
significantly higher incidence of late AMD than women (age-adjusted
odds ratio [OR], 2.97). The incidence of both early and late AMD
increased significantly with age. Multiple logistic regression
analysis showed that older age (per 1 year; OR, 1.10), smoking habits
(OR, 3.98), and higher circulating white blood cell (WBC) count (per
1000 cells/mm3) (OR, 1.38) were significantly associated with the
development of late AMD.
Discussion and Conclusions
This is the first population-based cohort study to investigate the
long-term incidence and risk factors for AMD in Japan. The findings
showed that the overall, 9-year, cumulative incidence of early AMD was
10.0%, and that of late AMD was 1.4%. Both incidences increased with
advancing age. Progression to late AMD was approximately 4.4% among
persons with early AMD. On multivariate analysis, smoking and higher
circulating WBC count were independently associated with the
development of late AMD.
It is reported that the 10-year cumulative incidence of early AMD was
12.1% in the Beaver Dam Eye Study in the United States and 14.1% in
the Blue Mountains Eye Study in Australia, both of which focused on a
white population. The Barbados Eye Study of the predominantly black
population of African descent reported a 9-year incidence of early AMD
of 12.6%. The 9-year incidence of early AMD in the current study
(10.0%) was somewhat lower than these other studies. Early AMD is less
common among the Japanese population than among white people and black
people in Western countries. This difference in the incidence of early
AMD among these studies could be due to the differences in study
participants' characteristics (e.g., age and proportion of gender
among studies), to dietary factors, to genetic factors, or perhaps to
the differences in methodology among these studies.
The incidence of late AMD in the current study (1.4%) was lower than
that reported in studies performed in white populations (Beaver Dam
Eye Study: 2.1%; Blue Mountains Eye Study: 3.7%) but was higher than
that found in the Barbados Eye Study (0.7%), which focused on a black
population. This suggests that late AMD is less common among the
Japanese compared with white people, and it is more common among the
Japanese compared with black people. The reason for different
incidences among different races is not clear. Previous research has
reported that increased ocular pigmentation (iris color and fundus
pigmentation) tends to decrease the risk of developing AMD. Racial
difference in late AMD incidence could be due to the differences in
ocular pigmentation, or perhaps to genetic factors.
In the current study, the 9-year incidence of neovascular AMD was
1.4%, and that of geographic atrophy was 0.04%. In contrast, the Blue
Mountains Eye Study has reported that the 10-year incidence of
neovascular AMD was 2.2%, and that of geographic atrophy was 1.7%. The
reason for the different incidence of geographic atrophy between
Japanese and white population, is not clear. It could be due to the
differences in environmental exposure or genetic factors among races.
This study found a significantly higher incidence of late AMD in men
than in women. In contrast, most studies conducted in Western, white
populations have shown a higher prevalence of late AMD in women. The
reason for this difference is precisely unknown, but smoking habits,
which are known to be a major risk factor for AMD, are likely to
contribute to a higher incidence of late AMD in Japanese men, because
the proportion of habitual smoking is much higher for men than women
in Japan.
The results of this study provide prospective evidence that cigarette
smoking increases the risk of developing late AMD. Compared with those
who never smoked, those who had smoked in the past or were currently
smoking had approximately a 4.0 times higher risk of late AMD, after
adjusting for other potential risk factors.
This study found that a higher WBC count was associated with incident
late AMD, independent of age, gender, and smoking status. A similar
association was also observed in the Blue Mountains Eye Study. Several
recent experimental evidences suggest that the association between
higher WBC count and late AMD is plausible, including the role of
inflammatory mechanisms in subretinal neovascularization and drusen
development.
In conclusion, the results of this study suggest that early and late
AMD is less common among the Japanese compared with white people in
Western countries, although late AMD is more common among the Japanese
compared with black people, and that older age, smoking habits and
higher WBC count are relevant risk factors for late AMD in the
Japanese.
Ophthalmology. 2009 Nov;116(11):2135-40
http://www.ncbi.nlm.nih.gov/pubmed/19744734
======================
ABOVE IS A PLAIN TEXT REPRODUCTION OF A NEWS STORY THAT APPEARS ON
MYVISIONTEST.COM. ANY HYPERLINKS, IMAGES, TABLES, OR OTHER
ENHANCEMENTS HAVE BEEN REMOVED. TO VIEW THE ORIGINAL VISIT THE BELOW
LINK.
http://www.myvisiontest.com/newsarchive.php?id=1029
the Japanese is lower than among white people in Western countries,
and is higher than among black people, according to a new study.
The pathogenesis of AMD remains poorly understood. It is thus very
important to determine the precise incidence of AMD and to identify
its risk factors to develop preventive measures of the disease. To
date, several population-based studies, have provided valuable
information on incidence and risk factors for AMD. The risk factors
examined include iris color, hypertension, atherosclerosis, smoking
habits, higher total/high-density lipoprotein ratio, and higher white
blood cell (WBC) count. However, information on the long-term risk of
AMD is scarce and nonexistent in Asians, including Japanese.
Methods and Results
In 1998, a total of 1775 residents of Hisayama, Japan aged ≥40 years
underwent a baseline eye examination. Of those, 1401 subjects (78.9%)
took part in the follow-up eye examination in 2007 and were enrolled
in the present study.
At both time points, the characteristics of AMD were determined by
grading color fundus photographs using the Wisconsin Age-Related
Maculopathy Grading System.
The age-standardized, 9-year cumulative incidence of early AMD was
10.0%, and that of late AMD was 1.4%. Men were found to have a
significantly higher incidence of late AMD than women (age-adjusted
odds ratio [OR], 2.97). The incidence of both early and late AMD
increased significantly with age. Multiple logistic regression
analysis showed that older age (per 1 year; OR, 1.10), smoking habits
(OR, 3.98), and higher circulating white blood cell (WBC) count (per
1000 cells/mm3) (OR, 1.38) were significantly associated with the
development of late AMD.
Discussion and Conclusions
This is the first population-based cohort study to investigate the
long-term incidence and risk factors for AMD in Japan. The findings
showed that the overall, 9-year, cumulative incidence of early AMD was
10.0%, and that of late AMD was 1.4%. Both incidences increased with
advancing age. Progression to late AMD was approximately 4.4% among
persons with early AMD. On multivariate analysis, smoking and higher
circulating WBC count were independently associated with the
development of late AMD.
It is reported that the 10-year cumulative incidence of early AMD was
12.1% in the Beaver Dam Eye Study in the United States and 14.1% in
the Blue Mountains Eye Study in Australia, both of which focused on a
white population. The Barbados Eye Study of the predominantly black
population of African descent reported a 9-year incidence of early AMD
of 12.6%. The 9-year incidence of early AMD in the current study
(10.0%) was somewhat lower than these other studies. Early AMD is less
common among the Japanese population than among white people and black
people in Western countries. This difference in the incidence of early
AMD among these studies could be due to the differences in study
participants' characteristics (e.g., age and proportion of gender
among studies), to dietary factors, to genetic factors, or perhaps to
the differences in methodology among these studies.
The incidence of late AMD in the current study (1.4%) was lower than
that reported in studies performed in white populations (Beaver Dam
Eye Study: 2.1%; Blue Mountains Eye Study: 3.7%) but was higher than
that found in the Barbados Eye Study (0.7%), which focused on a black
population. This suggests that late AMD is less common among the
Japanese compared with white people, and it is more common among the
Japanese compared with black people. The reason for different
incidences among different races is not clear. Previous research has
reported that increased ocular pigmentation (iris color and fundus
pigmentation) tends to decrease the risk of developing AMD. Racial
difference in late AMD incidence could be due to the differences in
ocular pigmentation, or perhaps to genetic factors.
In the current study, the 9-year incidence of neovascular AMD was
1.4%, and that of geographic atrophy was 0.04%. In contrast, the Blue
Mountains Eye Study has reported that the 10-year incidence of
neovascular AMD was 2.2%, and that of geographic atrophy was 1.7%. The
reason for the different incidence of geographic atrophy between
Japanese and white population, is not clear. It could be due to the
differences in environmental exposure or genetic factors among races.
This study found a significantly higher incidence of late AMD in men
than in women. In contrast, most studies conducted in Western, white
populations have shown a higher prevalence of late AMD in women. The
reason for this difference is precisely unknown, but smoking habits,
which are known to be a major risk factor for AMD, are likely to
contribute to a higher incidence of late AMD in Japanese men, because
the proportion of habitual smoking is much higher for men than women
in Japan.
The results of this study provide prospective evidence that cigarette
smoking increases the risk of developing late AMD. Compared with those
who never smoked, those who had smoked in the past or were currently
smoking had approximately a 4.0 times higher risk of late AMD, after
adjusting for other potential risk factors.
This study found that a higher WBC count was associated with incident
late AMD, independent of age, gender, and smoking status. A similar
association was also observed in the Blue Mountains Eye Study. Several
recent experimental evidences suggest that the association between
higher WBC count and late AMD is plausible, including the role of
inflammatory mechanisms in subretinal neovascularization and drusen
development.
In conclusion, the results of this study suggest that early and late
AMD is less common among the Japanese compared with white people in
Western countries, although late AMD is more common among the Japanese
compared with black people, and that older age, smoking habits and
higher WBC count are relevant risk factors for late AMD in the
Japanese.
Ophthalmology. 2009 Nov;116(11):2135-40
http://www.ncbi.nlm.nih.gov/pubmed/19744734
======================
ABOVE IS A PLAIN TEXT REPRODUCTION OF A NEWS STORY THAT APPEARS ON
MYVISIONTEST.COM. ANY HYPERLINKS, IMAGES, TABLES, OR OTHER
ENHANCEMENTS HAVE BEEN REMOVED. TO VIEW THE ORIGINAL VISIT THE BELOW
LINK.
http://www.myvisiontest.com/newsarchive.php?id=1029
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