MyVisionTest News Archive
Nov 25, 2009
AMD in Japan
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.
Read more...
Ophthalmology. 2009 Nov;116(11):2135-40
Tags: tobacco, racial differences, Japan, AMD
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.
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.
Read more...
Ophthalmology. 2009 Nov;116(11):2135-40
