Background
In the past decades, China has experienced one of the fastest ageing processes in the world. Alongside the demographic transition, there is a dramatic increase in age-related disability. Currently, vision loss is the leading cause of age-related disability in developing countries. Age-related eye diseases (AREDs), mainly including age-related macular degeneration (AMD), glaucoma, cataract and diabetic retinopathy, are primarily degenerative diseases in older people, whose burden is expected to increase with demographic ageing. This thesis aims to estimate the prevalence and burden of AREDs in China.
Methods
I searched three Chinese and three English bibliographic databases, namely China National Knowledge Infrastructure (CNKI), Wanfang, Chinese Biomedicine Literature Database (CBM-SinoMed), PubMed, Embase and Medline for studies of the prevalence of age-related macular degeneration (AMD), cataract, glaucoma, and diabetic retinopathy (DR) in China. For diseases where a single study could contribute multiple stratum-specific (e.g. age-specific and sex-specific) data points, a multilevel mixed-effects meta-regression was applied to generate the stratum-specific prevalence estimates of disease. For diseases where only study-level prevalence estimates were available, a random-effects meta-analysis was conducted to generate the pooled prevalence. By applying the estimated stratum-specific prevalence (or pooled prevalence) to the corresponding population data, available from the United Nations Population Division (UNPD), the national number of affected people was determined. By taking the geographic effects, the national number of cases was finally distributed into the six geographic regions (East China, North China, Northeast China, Northwest China, South Central China, Southwest China) in China.
Results
For estimating the prevalence and burden of AMD, 25 eligible studies were identified in the systematic review. The prevalence of any AMD ranged from 2.44% (95% CI: 1.85-3.22) in people aged 45-49 years to 18.98% (95% CI: 15.05-23.66) in people aged 85-89 years.
Prevalence of early AMD ranged from 1.79% (95% CI: 1.05-3.02) to 10.05% (95% CI: 6.17-15.97), and, in the case of late AMD, from 0.38% (95% CI: 0.16-0.97) to 3.88% (95% CI: 1.68-9.13). In late AMD, the prevalence of geographic atrophy (GA) was 0.15% (95% CI: 0.05-0.47) in people aged 45-49 years and 1.09% (95% CI: 0.35-3.36) in those aged 85-89 years, and the prevalence of neovascular AMD (NVAMD) ranged between 0.24% (95% CI: 0.11-0.50) and 2.79% (95% CI: 1.33-5.77). In people aged 45-89 years, the number of people with any AMD was 12.01 million (95% CI: 9.29-15.46) in 1990 and 26.65 million (95% CI: 20.62-34.27) in 2015. Within the same period, the number of people with early AMD increased from 9.44 million (95% CI: 7.74-11.15) to 20.91 million (95% CI: 17.16-24.68), and those with late AMD rose from 2.58 million (95% CI: 1.56-4.30) to 5.74 million (95% CI: 3.46-9.59). In late AMD, the number of people living with GA ranged from 0.87 million (95% CI: 0.40-1.83) in 1990 to 1.93 million (95% CI: 0.89-4.08) in 2015, and NVAMD from 1.71 million (95% CI: 1.16-2.47) to 3.81 million (95% CI: 2.57-5.51). It is projected the number of people with any AMD in 2050 will be 55.19 million (95% CI: 43.04-70.30). Among different regions, the South Central owed the most AMD cases (5.50 million in 2000 and 7.52 million in 2010), whereas North-West China the least (0.66 million in 2000 and 0.95 million in 2010).
For estimating the prevalence and burden of glaucoma, 30 studies met the inclusion criteria in the systematic review. In males, the prevalence of POAG ranged from 0.74% (95% CI: 0.48-1.14) in individuals aged 45-49 years to 3.02% (95% CI: 1.92-4.73) in those aged 85-89 years. The prevalence of POAG in females was slightly lower than that in males across the whole age spectrum from 45 to 89 years, ranging from 0.54% (95% CI: 0.35-0.84) to 2.24% (95% CI: 1.41-3.53). For PACG, the prevalence increased from 0.48% (95% CI: 0.39-0.60) in males aged 45-49 years to 3.44% (95% CI: 2.66-4.45) in males aged 85-89 years. The prevalence of PACG was consistently higher in females than in males, ranging from 0.91% (95% CI: 0.74-1.11) in females aged 45-49 years to 6.33% (95% CI: 4.98-8.02) in females aged 85-89 years. The pooled prevalence of secondary glaucoma was 0.15% (95% CI: 0.10-0.23). In people aged 45-89 years, the number of people affected by POAG increased from 2.35 million (95% CI: 1.54-3.60) in 1990 to 5.22 million (95% CI: 3.40-7.98) in 2015, PACG from 3.22 million (95% CI: 2.70-3.84) to 7.14 million (95% CI: 5.97-8.53), and secondary glaucoma from 0.34 million (95% CI: 0.23-0.53) to 0.76 million (95% CI: 0.51-1.17). In 2015, more than half (54.42%) of the glaucoma cases were PACG, followed by POAG (39.79%) and secondary glaucoma (5.79%). By 2050, the number of all glaucoma cases in China will be 25.16 million (95% CI: 18.96-33.86). %). In both 2000 and 2010, East China owed the most POAG cases (1.02 million in 2000 and 1.39 million in 2010) and PACG cases (1.24 million in 2000 and 1.68 million in
2010), whereas Northwest China the least (POAG: 0.19 million in 2000 and 0.27 million in 2010; PACG: 0.32 million in 2000 and 0.46 million in 2010).
For estimating the prevalence and burden of cataract and cataract blindness, 55 studies met the eligibility criteria and were included in the systematic review and meta-analysis. In males, the prevalence of any cataract (including post-surgical cases) ranged from 6.71% (95% CI: 5.06-8.83) in people aged 45-49 years to 73.01% (95% CI: 65.78-79.2) in elderly aged 85-89 years. In females, the prevalence of any cataract increased from 8.39% (95% CI: 6.36-10.98) in individuals aged 45-49 years to 77.51% (95% CI: 71.00-82.90) in those aged 85-89 years. For age-related cataract (ARC, including post-surgical cases), in males, the prevalence rates ranged from 3.23% (95% CI: 1.51-6.80) in adults aged 45-49 years to 65.78% (95% CI: 46.72-80.82) in those aged 85-89 years. The prevalence of ARC in females was 4.72% (95% CI: 2.22-9.76) in the 45-49 years age group and 74.03% (95% CI: 56.53-86.21) in the 85–89 years age group. The pooled prevalence rate of cataract blindness (including post-surgical cases) by best corrected visual acuity (BCVA) <0.05 among middle-aged and older Chinese was 2.30% (95% CI: 1.72-3.07), and those of cataract blindness by BCVA <0.10 and cataract blindness by presenting visual acuity (PVA) <0.10 were 2.56% (95% CI: 1.94-3.38) and 4.51% (95% CI: 3.53-5.75) respectively. In people aged 45-89 years, the number of any cataract cases was 50.75 million (95% CI: 42.17-60.37) in 1990 and 111.74 million (95% CI: 92.94-132.84) in 2015, and that of ARC rose from 35.77 million (95% CI: 19.81-59.55) in 1990 to 79.04 million (95% CI: 44.14-130.85) in 2015. By 2050, it is projected that the number of people (45-89 years of age) affected by any cataract will be 240.83 million (95% CI: 206.07-277.35), and that of those with ARC will be 187.26 million (95% CI: 113.17-281.23). During 2000 and 2010, South Central China consistently owed the most cases of any cataract (23.50 million in 2000 and 31.79 million in 2010), whereas Northwest China the least (3.37 million in 2000 and 4.87 million in 2010).
For estimating the prevalence and burden of DR. A total of 31 studies provided information on the prevalence of DR and 21 explored potential risk factors for DR. The pooled prevalence of any DR, nonproliferative DR (NPDR) and proliferative DR (PDR) was 1.14% (95% CI: 0.80-1.52), 0.90% (95% CI: 0.56-1.31) and 0.07% (95% CI: 0.02-0.14) in general population; In people with DM, the pooled prevalence rates were 18.45% (95% CI:14.77-22.43), 15.06% (95% CI:11.59-18.88) and 0.99% (95% CI: 0.40-1.80) for any DR, NPDR and PDR, respectively. The prevalence of any DR in DM patients peaked between 60 and 69 years of age, and increased steeply with the duration of DM. DM patients residing in rural China were at a higher risk to have DR than those in urban areas. In addition, insulin treatment, elevated
FBG level and higher HbA1c concentration were confirmed to be associated with a higher prevalence of DR in people with DM, with meta-ORs of 1.99 (95% CI: 1.34-2.95), 1.33 (95% CI: 1.12-1.59) and 1.15 (95% CI: 1.09-1.20) respectively. In 2010, a total of 13.16 million (95% CI: 8.95-18.00) Chinese aged 45 years and above were living with DR, among whom the most were in South Central China (3.71 million) and the least were in Northwest China (0.87 million).
Conclusions
This thesis presents a comprehensive estimation of the prevalence and burden of AREDs in China. With the dramatic ageing trend in the next three decades, the prevalence and burden of AREDs will continue to increase. More elaborate epidemiological studies are still required for better estimation of the disease burden of AREDs. Primary and secondary prevention, treatment and effective government response are urgently needed to optimise public health strategies for mitigating this important health problem
