Prevalence of Age-Related Macular Degeneration in China: An Epidemiological Overview

 

By 2050, the number of people in China with AMD is projected to exceed 55 million.

Age-related macular degeneration (AMD) stands as a primary cause of irreversible vision loss and blindness in the global elderly population. Its significance as a public health concern is escalating with the increasing lifespan of populations worldwide, leading to a substantial rise in the number of affected individuals. Given China's position as the most populous nation with a rapidly expanding elderly demographic, understanding the prevalence of AMD within its borders is of paramount importance. Accurate epidemiological data is essential for effective public health planning, the allocation of healthcare resources, the development of targeted interventions, and for comprehending the broader socioeconomic impact of this debilitating condition.

Several systematic reviews and meta-analyses have sought to establish the prevalence of AMD in Chinese populations. One such study by Xu et al. (2019) examined data from nine studies encompassing 29,344 individuals, revealing a crude pooled prevalence of early AMD at 4.9% (95% CI: 3.1%-7.7%) and late AMD at 0.7% (95% CI: 0.5%-1.1%) among Chinese individuals aged 50 years and above across the globe. This analysis incorporated studies conducted in mainland China, Taiwan, Singapore, and the United States. In contrast, a comprehensive systematic review and meta-analysis by Zhang et al. (2017), which specifically focused on mainland China and included 25 studies, reported a wider range of prevalence for any AMD, spanning from 2.44% (95% CI = 1.85-3.22) in the 45-49 year age group to a considerably higher 18.98% (95% CI = 15.05-23.66) in those aged 85-89 years. The observed differences in pooled prevalence between these analyses could stem from variations in inclusion criteria, the timeframes of the included studies, and potential inconsistencies in diagnostic criteria and grading systems employed across different research efforts. Furthermore, the Jiangning Eye Study (2014), a population-based investigation in urban Shanghai, indicated an age-standardized prevalence of early AMD at 9.5% (95% CI, 8.2-10.8) and late AMD at 1.0% (95% CI, 0.5-1.5) in individuals aged 50 years or older.

Delving into the prevalence of different stages of AMD, the meta-analysis by Zhang et al. (2017) provided detailed age-specific rates for early AMD, ranging from 1.79% (95% CI = 1.05-3.02) in the 45-49 age group to 10.05% (95% CI = 6.17-15.97) in the 85-89 age group. For late AMD, the prevalence similarly increased with age, from 0.38% (95% CI = 0.16-0.97) to 3.88% (95% CI = 1.68-9.13) for the same age ranges. Within late AMD, the subtypes of geographic atrophy (GA) and neovascular AMD (NVAMD) also exhibited age-related increases in prevalence. GA ranged from 0.15% in the 45-49 year group to 1.09% in the 85-89 year group, while NVAMD prevalence spanned from 0.24% to 2.79% across the same age cohorts. In contrast to prevalence data, the Tongren Health Care Study (2024) reported the 5-year incidence of AMD in an adult Chinese population with a mean age of 54.9 years, finding an incidence of 6.1% for any AMD, 5.0% for early AMD, 3.4% for intermediate AMD, and 0.3% for late AMD. Notably, the Yangxi Eye Study (2017), conducted in rural southern China, revealed a considerably higher age-standardized prevalence of early AMD (40.4%), intermediate AMD (17.6%), and late AMD (0.79%) in individuals aged 50 years or older. AMD is generally classified into early, intermediate, and late stages based on the presence and characteristics of drusen, which are small deposits under the retina, and the presence of pigmentary abnormalities.

The prevalence of AMD in China demonstrates a strong positive correlation with age, a trend consistently observed across various studies. The meta-analysis by Zhang et al. (2017) clearly illustrates this pattern for any, early, and late AMD across the age spectrum from 45-49 to 85-89 years. The Jiangning Eye Study (2014) further supports this, reporting age-standardized prevalence rates in individuals aged 50 years and above. In Hunan China, a study indicated an age-standard frequency of early AMD of 6.6% in those over 60 years of age. Global analyses also corroborate this trend, showing that prevalence rates in China generally increase after the age of 50-54, reaching their peak in the oldest age groups (90-94 and above). The Chinese American Eye Study (2016) reported a similar age-related increase in prevalence among Chinese Americans, ranging from 5.8% in the 50-59 year group to 17.6% in individuals 80 years and older.

Age Group	Prevalence of Any AMD (95% CI)	Prevalence of Early AMD (95% CI)	Prevalence of Late AMD (95% CI)
45-49	2.44% (1.85-3.22)	1.79% (1.05-3.02)	0.38% (0.16-0.97)
50-54	3.15% (2.34-4.23)	2.30% (1.43-3.68)	0.47% (0.20-1.08)
55-59	4.15% (3.10-5.54)	3.03% (1.87-4.88)	0.63% (0.27-1.46)
60-64	5.47% (4.11-7.25)	3.99% (2.44-6.48)	0.83% (0.36-1.92)
65-69	7.19% (5.41-9.51)	5.24% (3.18-8.59)	1.10% (0.47-2.56)
70-74	9.46% (7.12-12.47)	6.90% (4.10-11.38)	1.52% (0.65-3.57)
75-79	12.44% (9.34-16.38)	9.07% (5.33-15.01)	2.12% (0.91-4.92)
80-84	16.36% (12.27-21.69)	11.94% (6.81-20.85)	2.98% (1.28-6.91)
85-89	18.98% (15.05-23.66)	10.05% (6.17-15.97)	3.88% (1.68-9.13)

 

Significant regional variations in AMD prevalence have been observed within China. The Yangxi Eye Study (2017) in rural southern China reported a remarkably higher prevalence of early and intermediate AMD compared to studies conducted in urban areas such as Beijing and Shanghai. The age-standardized prevalence in Yangxi reached 40.4% for early AMD and 17.6% for intermediate AMD, figures substantially exceeding those reported elsewhere in mainland China. Conversely, the Jiangning Eye Study (2014) in urban Shanghai found an age-standardized prevalence of early AMD (9.5%) and late AMD (1.0%) that was elevated compared to the older Beijing and Handan studies, suggesting potential differences even among urban centers or changes over time. A study by Zhou et al. (2023), analyzing data from 17 provinces across China in 2021, also identified regional differences in AMD prevalence, although a clear geographical trend was not apparent.The adjusted prevalence of AMD in this study was reported as 13.93 cases per 1000 population. Furthermore, the meta-analysis by Zhang et al. (2017) estimated the regional distribution of AMD cases in China for the years 2000 and 2010, indicating that the South Central region bore the highest number of cases, while the North-West region had the fewest.

Analyzing trends in AMD prevalence over time reveals a complex picture. While the study by Zhang et al. (2017) indicated a slight decrease in the national prevalence of any AMD, early AMD, and late AMD between 1990 and 2015, it is crucial to note that the absolute number of affected individuals increased dramatically due to the country's aging population. Conversely, the Global Burden of Disease study reported a significant increase in the all-age number and rate of AMD prevalence in China from 1990 to 2019. Although the age-standardized DALYs rate showed a slight decrease, the age-standardized prevalence increased during this period. Globally, East Asia, including China, experienced the most notable rise in AMD prevalence between 1990 and 2019. Projections from Zhang et al. (2017) estimate a substantial surge in the number of AMD cases in China by 2050, potentially exceeding 55 million

When comparing AMD prevalence in China with other populations, meta-analyses suggest that both early and late AMD are less common in Chinese populations worldwide compared to Caucasian populations aged 50 years and above. Global estimates also indicate that early AMD is generally less prevalent in Asian populations, including Chinese individuals, than in European populations. However, some studies propose that the prevalence of AMD in older Asians, including Chinese, can be comparable to that of white populations. Notably, Zhou et al. (2023) found that the incidence rate of early AMD was highest among White individuals, followed by Chinese and Spanish individuals, with the lowest rates in Black individuals. Interestingly, Wang et al. (2019) highlighted that Asian populations, particularly the Chinese, exhibit a higher susceptibility to the neovascular or exudative form of AMD compared to Caucasians. The Chinese American Eye Study (2016) reported an age-adjusted prevalence in Chinese Americans that aligned with estimates from mainland China and Taiwan, suggesting a potential interplay of genetic and environmental factors

The burden of AMD in China is substantial and projected to grow significantly. Estimates from Zhang et al. (2017) indicate that the number of individuals affected by any form of AMD in China rose from 12.01 million in 1990 to 26.65 million in 2015, with projections suggesting a figure of 55.19 million by 2050. The number of people with early and late AMD also experienced significant increases during this period. The Global Burden of Disease study revealed a marked increase in Disability-Adjusted Life Years (DALYs) attributable to AMD in China from 1990 to 2019, underscoring the considerable impact of the disease on healthy life expectancy. In 2019, China had the largest population of individuals living with AMD globally, a consequence of its large population and increasing longevity. Among neighboring countries in 2019, China ranked second in terms of age-standardized prevalence rate of AMD. Consistently, studies have shown that females in China experience a higher prevalence and burden (DALYs) of AMD compared to males across various age groups.

In conclusion, the prevalence of AMD in China represents a significant and growing public health concern. While overall prevalence rates might appear lower compared to some other ethnicities, the sheer size and aging trend of the Chinese population translate to a substantial number of affected individuals, a number projected to increase dramatically in the coming decades. Notable regional variations exist within China, with rural southern China exhibiting particularly high rates of early and intermediate AMD. The increasing burden of AMD necessitates a multi-faceted public health approach encompassing enhanced public awareness, the implementation of effective screening programs targeting high-risk age groups, and ensuring equitable access to appropriate treatment options, particularly for the more severe neovascular form of the disease which appears to be more prevalent in Chinese populations. Further research is crucial to elucidate the underlying genetic and environmental factors contributing to AMD in different regions and demographic groups within China. Standardizing epidemiological studies through the consistent use of recognized grading systems will be essential for obtaining more reliable and comparable data to inform evidence-based public health policies and resource allocation strategies aimed at mitigating the impact of this leading cause of vision loss.

Summary:

 

References:

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