Abstract
The current epidemic status of diabetic retinopathy in China is unclear. A national prevalence survey of diabetic complications was conducted. 50,564 participants with gradable non-mydriatic fundus photographs were enrolled. The prevalence rates (95% confidence intervals) of diabetic retinopathy and vision-threatening diabetic retinopathy were 16.3% (15.3%–17.2%) and 3.2% (2.9%–3.5%), significantly higher in the northern than in the southern regions. The differences in prevalence between those who had not attained a given metabolic goal and those who had were more pronounced for Hemoglobin A1c than for blood pressure and low-density lipoprotein cholesterol. The participants with vision-threatening diabetic retinopathy had significantly higher proportions of visual impairment and blindness than those with non-vision-threatening diabetic retinopathy. The likelihoods of diabetic retinopathy and vision-threatening diabetic retinopathy were also associated with education levels, household income, and multiple dietary intakes. Here, we show multi-level factors associated with the presence and the severity of diabetic retinopathy.
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Introduction
Diabetic retinopathy (DR), a major specific diabetic microvascular complication, occurs in approximately one-third of patients with diabetes1. Although DR is often insidious and asymptomatic at the early stages, it might quickly progress into vision-threatening DR (VTDR) without awareness and intervention, and then could lead to irreversible vision impairment. About one-third of patients with proliferative DR (PDR) combined with high-risk characteristics will progress into severe vision loss within three years if not treated promptly2. In many countries, DR is a leading cause of preventable vision impairment and blindness in the working-age population3. Meanwhile, DR was the only one of the top five causes of blindness that had a globally increased age-standardized prevalence in adults aged 50 years and older between 1990 and 2020, and its prevalence was projected to continue rising, with an increasing number of patients with diabetes and longer life expectancy4. Vision impairment and blindness severely affect the patient’s quality of life, increase the incidence risks of comorbidities5, and reduce life expectancy. However, early systematic screening and timely treatment for DR have been shown to be highly effective in avoiding vision impairment and blindness6. With the largest number of people with diabetes, around one-fourth of the global number, living in China, there is a lack of current data representing a national distribution of DR to guide the prevention and control strategy7.
As we know, so far only two multiple province-level (12-province and 6-province) prevalence surveys of DR were conducted in China8,9. However, the two studies lacked a sampling design and their participants were recruited from both hospitals and communities, which resulted in the samples being unrepresentative of Chinese people with diabetes. In recent years, significant changes in factors related to DR, including socio-economic development, lifestyle, dietary patterns, retinal imaging, and treatment, may have affected the epidemiologic features of DR10,11. For these reasons, the experts call for continuous high-quality population-based studies12, and updated nationally representative surveys are also urgently needed to guide the prevention of vision impairment and blindness among patients with diabetes in China.
In this work, we report the distributions of any DR and VTDR nationwide as well as potentially associated factors regarding demographics, geographical regions, socio-economic status, lifestyle factors, and clinical characteristics among Chinese adults with diagnosed diabetes, based on the national survey of diabetic complications in China between 2018 and 2020. An in-depth understanding of the related factors of DR help promote better medical care, a healthier lifestyle, and potential causal research.
Results
Characteristics of study participants
For the 50,564 participants, the median (25th percentile-75th percentile) age and diabetes duration were 57.5 years (50.9–64.8) and 5.2 years (2.5–10.1), respectively. Of these participants, 50.3% were females, 49.2% resided in the northern regions, and 46.8% resided in rural areas. The treatment rates for hyperglycemia, hypertension, and dyslipidemia were 78.6%, 39.1%, and 12.3%, respectively, and the corresponding attainment rates of Hemoglobin A1c (HbA1c), Blood pressure (BP), and low-density lipoprotein cholesterol (LDL-C) targets were 44.0%, 29.8%, and 34.9%, respectively (Table 1). Compared with the participants without DR, those with any DR had significantly higher proportions of northerners and longer diabetes duration, but lower education and income levels. The participants with any DR had a higher treatment rate for lowering glucose and comparable treatment rates for hypertension and dyslipidemia, but they still had higher levels of blood glucose, systolic blood pressure, and LDL-C (all p < 0.050) (Table 1). Furthermore, similar linear trends were also observed for the above-mentioned characteristics as the severity of DR increased in Supplementary Table 1. Notably, only 13.6% of the 8559 participants with any DR (9.4% of participants with non-VTDR and 32.8% of participants with VTDR) reported a history of DR (Table 1 and Supplementary Table 1).
In addition, there were differences in lifestyle factors, including physical activity, unhealthy behaviors (smoking and alcohol drinking), and multiple diet intakes between the two comparison groups (Table 1).
Prevalence of DR and VTDR
The weighted prevalence of any DR and VTDR among Chinese adults with diabetes grouped by demographic factors and diabetes duration, as well as by the attainment of metabolic targets, were separately shown in Table 2 and Table 3.
In the patients with diabetes aged 18–74 years, the overall prevalence of any DR was 16.3% (95% CI 15.3%–17.2%), including the prevalence of 0.75% (95% CI 0.64%–0.86%) for diabetic macular edema (DME); and the prevalence of VTDR was 3.2% (95% CI 2.9%–3.5%), including 2.3% (95% CI 2.1%–2.6%), 0.64% (95% CI 0.55%–0.73%), and 0.54% (95% CI 0.45%–0.63%) for severe non-proliferative DR (NPDR), PDR and clinically significant macular edema (CSME), nationwide, respectively. It was estimated that roughly 19.5 million and 3.8 million adults with diagnosed diabetes had any DR and VTDR, respectively, in China (Table 2).
Among the adults with diabetes, the inter-subgroup differences in the prevalence of any DR and VTDR between men and women or between urban residents and rural residents did not reach statistical significance. The prevalence of any DR and VTDR was significantly higher in the northern than in the southern regions (DR: 18.1% [95% CI 16.6%–19.6%] vs. 14.4% [95% CI 13.3%–15.5%]; VTDR: 3.8% [95% CI 3.4%–4.3%] vs. 2.5% [95% CI 2.2%–2.8%]). The prevalence of any DR and VTDR was 8.2% (95% CI 6.7%–9.7%) and 1.24% (95% CI 0.49%–2.00%) among those with diabetes duration of less than one year and climbed to 38.6% (95% CI 35.8%–41.4%) and 13.8% (95% CI 11.9%–15.6%) among those with diabetes duration of longer than 20 years, respectively (Table 2).
The differences in proportions of any DR and VTDR were statistically significantly higher in those with worse metabolic control versus those with better control (for HbA1c, any DR: 22.3% [95% CI 21.1%–23.4%] vs. 8.7% [95% CI 7.8%–9.6%], VTDR: 4.6% [95% CI 4.2%–5.0%] vs. 1.4% [95% CI 1.1%–1.6%]; for BP, any DR: 17.5% [95% CI 16.5%–18.5%] vs. 13.7% [95% CI 12.5%–14.9%], VTDR: 3.4% [95% CI 3.1%–3.7%] vs. 2.7% (95% CI 2.3%–3.1%); for LDL-C, any DR: 16.7% [95% CI 15.7%–17.8%] vs. 15.4% [95% CI 14.3%–16.5%]) (Table 3).
For the 31 provinces in mainland China, the standardized province-specific prevalence of any DR and VTDR among the adults with diabetes ranged from 9.9% (95% CI 8.3%–11.5%) for Guizhou to 29.1% (95% CI 26.5%–31.6%) for Shandong, and 1.27% (95% CI 0.61%–1.94%) for Jiangxi to 6.3% (95% CI 5.1%–7.5%) for Heilongjiang, respectively. The top 3 provinces for the prevalence of any DR or VTDR, all in the northern regions, were Shandong, followed by Heilongjiang (27.0% [95% CI 24.5%–29.5%]) and Henan (24.6% [95% CI 22.3%–26.8%]) for any DR, and Heilongjiang, Shandong (6.2% [95% CI 5.0%–7.3%]), and Beijing (4.7% [95% CI 3.6%–5.9%]) for VTDR. Of note were the obvious inconsistencies between province-specific prevalence ranks of any DR and VTDR for individual provinces, such as Qinghai (Rank 4 of DR vs. Rank 23 of VTDR) (Table 4).
Visual impairment and blindness associated with DR and VTDR
The proportions of visual impairment and blindness were significantly higher in the participants with any DR than those without DR, and in the participants with VTDR than in those with non-VTDR (all p < 0.050). The rates of worse-seeing and better-seeing eye blindness among the patients with VTDR were 11.25-fold (95% CI 8.13–15.58) and 10.26-fold (95% CI 5.97–17.65) higher than those with non-VTDR, respectively, after adjustment for sex and age (Table 5).
Factors associated with prevalent DR, non-VTDR, and VTDR
Multivariable-adjusted analyses results assessing the factors associated with any DR and the severity of DR were shown in Table 6 (for demographic and clinical factors) and Table 7 (for lifestyle factors).
Females were less likely to have any DR, or non-VTDR and VTDR than males, with odds ratio (OR) (95% confidence interval [CI]) being 0.78 (0.69–0.87), 0.82 (0.72–0.92), and 0.63 (0.53–0.75), respectively. Age was only significantly negatively associated with VTDR (OR 0.98, 95% CI 0.97–0.99). The people with diabetes living in the northern region were more likely to have any DR (OR 1.39, 95% CI 1.22–1.58), non-VTDR (OR 1.35, 95% CI 1.17–1.55) and VTDR (OR 1.60, 95% CI 1.34–1.91) than those in the southern regions (Table 6).
As for socio-economic indicators, the lower likelihoods of having any DR, non-VTDR, and VTDR were found in the participants with education levels of high school and above, with ORs ranging from 0.77 (95% CI 0.61–0.96) to 0.84 (95% CI 0.74–0.95), and average annual household income per capita equal to or greater than 20,000 RMB, with ORs ranging from 0.65 (95% CI 0.53–0.81) to 0.79 (95% CI 0.69–0.91), than their counterparts (Table 6).
In terms of clinical characteristics, the participants with longer diabetes duration and family histories of diabetes showed significantly higher odds of any DR, non-VTDR, or VTDR (both p < 0.050). The participants who exhibited poor HbA1c or BP control had 2.25-fold or 1.30-fold higher likelihoods of having any DR, 2.17-fold or 1.29-fold higher odds of having non-VTDR, and 2.72-fold or 1.33-fold higher risks of having VTDR, respectively, than those with better controls. Nevertheless, there were no significant associations of LDL-C control with any DR, non-VTDR, or VTDR (Table 6).
Further, analyses on the association of physical activity and diet with any DR, non-VTDR, and VTDR found that physical activity over 600 metabolic equivalents (METs) minutes/week were significantly negatively associated with any DR (OR 0.88, 95% CI 0.77–0.99). In terms of diet, higher fresh fruit consumption (>100 g/day) was negatively associated with any DR (OR 0.85, 95% CI 0.77–0.95), as well as non-VTDR and VTDR with ORs of 0.87 (95% CI 0.77–0.99) and 0.77 (95% CI 0.63–0.95). Additionally, higher potato intake (>31 g/day) was negatively associated with any DR (OR 0.86, 95% CI 0.79–0.94) and non-VTDR (OR 0.84, 95% CI 0.78–0.91), and higher dairy product consumption (>100 ml/day) was only negatively associated with non-VTDR (OR 0.90, 95% CI 0.84–0.98). In contrast, higher refined grain consumption (>450 g/day) was positively associated with non-VTDR (OR 1.11, 95% CI 1.01–1.22) (Table 7).
In addition, a comparison of characteristics of Chinese adults with diabetes in the northern and southern regions was shown in Supplementary Table 2.
Discussion
Our study was the first to report a nationally representative prevalence of 16.3% (15.3%–17.2%) for any DR (16.2% [15.3%–17.1%] for DR and 0.75% [0.64%–0.86%] for DME) and 3.2% (2.9%–3.5%) for VTDR (2.3% [2.1%–2.6%] for severe NPDR, 0.64% [0.55%–0.73%] for PDR, and 0.54% [0.45%–0.63%] for CSME) in Chinese adults with diagnosed diabetes aged 18–74 years. The previous prevalence rates of DR derived from different studies were only used as rough references because there were differences in study methodologies and some details of individual studies were not provided. By pooling data from the population-based studies among adults with diabetes aged 20 and older, the global pooled prevalence, of 27 countries between 1980 and 2017, were 22.27% for any DR and 6.17% for VTDR12, and the national pooled prevalence for China, of 16 provinces between 1990 and 2017, were 18.45% for any DR and 0.99% for PDR13. A lower prevalence of any DR in China may be partly related to ethnic disparity, with Asians reported having a lower DR prevalence than the Hispanics12, Middle Easterners12, and Caucasians1, and that the diabetes epidemic commenced later in China than in some developed countries14,15.
Previous small-sample size local population-based surveys in Chinese with diabetes reported a significant discrepancy in the prevalence of DR with a range of 5.4%–41.7%13, which not only reflects differences in region-related factors, but is also probably due to different study designs, grading standards, and population characteristics. Based on the same methodologies, central blind grading, and unified quality control, our study reported national prevalence rates of DR and PDR slightly lower than the pooled rates for Chinese patients (16.3% vs. 18.45% for DR; 0.64% vs. 0.99% for PDR), and exhibited variations in province-specific prevalence of any DR from 9.9% to 29.1% and VTDR from 1.27% to 6.3% among Chinese adults with diabetes aged 18–74 years. This study showed that the top three province-specific prevalence of any DR and VTDR were all in the northern regions, and generally, a higher prevalence of any DR and VTDR was observed in the northern regions than in the southern regions. The north–south variation was in line with two meta-analysis studies regarding the regional distribution of DR in China13,16. Higher DR prevalence in rural than in urban areas reported by the two meta-analyses, was not seen in this study13,16. In general, the prevalence of DR in this study seemed slightly lower than that in the previous reports, which may be attributed to improved diabetes care and expanded screening coverage for DR to some extent. In addition, there seemed to be a decreasing trend in the prevalence of DR over time in China when comparing the prevalence rates between the two meta-analyses (from 23.0% between 1986 and 2009 to 18.45% between 1990 and 2017) and between the two multi-province surveys with participants from community health service centers and hospitals (from 34.08% between 2014 and 2015 to 30.1% between 2015 and 2018)8,9,13,16.
Some studies observed that DR was also found in patients with newly diagnosed diabetes, for example, 18% in patients with newly diagnosed T2DM in England17. Our study showed that the prevalence of any DR, especially VTDR and its subtypes, significantly increased with prolonged diabetes duration: the prevalence of any DR and VTDR reached 8.2% (6.7%–9.7%) and 1.24% (0.49%–2.00%) with diabetes duration of less than one year, and rose to 38.6% (35.8%–41.4%) and 13.8% (11.9%–15.6%) with diabetes duration of 20 years or more, respectively. A study showed that two years after the diagnosis of DR, the probabilities of sustained blindness in eyes with moderate NPDR, severe NPDR, and PDR were 2.6, 3.6, and 4.0 times higher than in eyes with mild NPDR, respectively18. In line with these results, our study observed that the proportions of worse-seeing and better-seeing eye blindness were 11.25-fold (95% CI 8.13–15.58) and 10.26-fold (95% CI 5.97–17.65) higher for patients with VTDR than those with non-VTDR. Regular screening for DR recommended by the American Diabetes Association and Chinese Diabetes Society and the establishment of a comprehensive eye screening system in China are necessary strategies to decrease vision loss caused by DR.
Consistent with the established knowledge, DR and VTDR were more prevalent among patients with worse control of glycemia and BP6. In this study, less than half of the participants achieved the recommended levels of HbA1c, BP, and LDL-C (44.0%, 29.8%, and 34.9%), lower than in US adults with diabetes between 1999 and 2018 (51.1%, 47.0%, and 53.3%)14. Hence, there is still much room for improvement in the metabolic management of patients with diabetes in China.
Our study showed that people with a family history of diabetes or living in northern China were more likely to have DR than their counterparts even after adjustment for multiple factors. Genetic background and shared environmental factors contributed to the susceptibility to DR. A family clustering study showed that genetic components seem to contribute more to the severity of DR than to the presence of DR19. In China, the Qinling–Huaihe line is the most commonly used line to divide the northern or southern regions. The two regions not only have significant differences in natural conditions and socio-cultural customs20, but also differences in physical features21 and genetic background22. Further exploration of the causes of geographical differences may provide more clues into possible genetic and environmental contributors to the etiology of DR.
Several socio-economic factors were also involved in the development of DR. Our study showed that participants educated to high school and above were less likely to have any DR, which emphasized the importance of improving the knowledge of diabetic prevention at the population levels. As a Canadian cohort study showed, low-income people were less likely to engage in preventive care and tended to have a higher prevalence and greater severity of DR23. Screening for DR is cost-effective, but it needs to address some barriers, such as acceptability, availability, and affordability. Artificial intelligence diagnostic systems are expected to offer a promising solution to this dilemma in the future24. Unfortunately, our study showed that the majority of people with DR (86.5% of the participants with any DR, 90.6% of participants with non-VTDR, and 67.2% of participants with VTDR) were undiagnosed before this survey.
Our findings also suggested that patients without DR had healthier dietary patterns than those without DR, with higher intakes of fresh fruits, potatoes, and dairy products, but a lower intake of refined grains. In particular, fresh fruit intakes were favorably associated with any DR and VTDR. Fresh fruits are an important source of essential vitamins, minerals, fiber, and flavonoids that can help decrease retinal injury25. However, in this study, the patients’ fruit intake was well below the recommended intake of the Dietary Guidelines for Chinese Residents (28.6 g/day vs 200.0 g/day). Therefore, healthy diet guidance for patients with diabetes needs to be on the agenda in China.
Our study has several strengths. Firstly, it was the national, population-based survey of DR with a multistage sampling scheme. Together with a systematic and comprehensive investigation of the associated risk factors, including not only information on socio-demographics, medical history, and clinical data, but also detailed information on lifestyle, it is then possible to describe multi-level factors associated with DR. Secondly, professional ophthalmologists checked the fundus photographs with unified criteria on one center. Several limitations require consideration. Firstly, the two-field fundus photography was used instead of optical coherence tomography, which may affect the accurate classification of DME. Also, this study is conducted in community health centers instead of being completed in specialized ophthalmology departments in hospitals. Due to limited resources, it is difficult to include the assessment of some ocular risk parameters for DR, like hyperopia or short axial length, in a large-scale epidemiology study. Secondly, a temporal relationship between exposure and outcome cannot be confirmed, and there were inevitable misreporting and recall biases. Thirdly, the differences between those with ungradable photos and those with gradable photos might introduce selection bias. But due to the very low proportion of ungradable photos (3.01%), the effect was minimal.
In conclusion, in China, approximately 19.5 million people with diabetes had any DR; of them, one-fifth are at the VTDR stage. With a large number of people with diabetes and an aging population in China comes the great challenge of avoiding visual impairment and blindness. Our study showed that multifaceted and tailored efforts to reduce the vision loss of patients with diabetes, including early and regular screening for DR, metabolic control improvement, educational improvement, lifestyle promotion, more care for these vulnerable and high-risk populations, and further exploration of geographical causes are necessary.
Methods
The study protocol was approved by the Ethics Committee of Shanghai Sixth People’s Hospital (Approval No: 2018-010) and was also registered in the Chinese Clinical Trial Registry (ChiCTR1800014432). All the study participants provided written informed consent before data collection.
The study protocol was published before26 and summarized briefly below.
Study design and study participants
The China National Diabetic Chronic Complications Study (China DiaChronic Study) was conducted to investigate the epidemiological characteristics of diabetes-related complications and the attainment rates of metabolic targets in adults with diagnosed diabetes in China between March 2018 and January 2020. All those recruited in this study were people with diabetes diagnosed by physicians in hospitals, registered in the diabetes management registration system of basic public health services27 in community health centers, and monitored by the local Center for Disease Control and Prevention. A multistage sampling scheme (stratification, clustering, and random selection) was designed based on the disease surveillance points of the China Chronic Disease and Risk Factors Surveillance (CCDRFS)28. 58560 participants aged 18–74 years were sampled from the diabetes management registration system of 488 neighborhoods/villages across 31 provinces, autonomous regions, and municipalities (referred to as provinces hereafter). A flowchart of the multistage sampling scheme was listed in the protocol of this study26. Briefly speaking, there are three sampling stages. In the first stage, four study sites based on the disease surveillance points or replaced study sites were selected from each province after considering urbanization levels. Finally, a total of 122 study sites (65 urban study sites and 57 rural study sites) were randomly selected and invited to participate. In the second stage, four neighborhoods in urban areas or four villages in rural areas were randomly selected from each study site, resulting in 260 neighborhoods and 228 villages in total. In the third stage, according to the age and gender structure of the CCDRFS 2013 diabetes data, the national sample size of 58,560 individuals and the sample size of 480 at each study site were set. 480 participants were randomly invited from those registered in the diabetes management registration system at each study site.
53,401 participants completed the interview with an overall response rate of 91.2%. Retinal photographs were not taken in 1267 participants and were of insufficient quality for grading in 1570 participants. The comparisons of general characteristics between the participants with gradable and ungradable photographs were presented in the Supplementary Table 3. Compared with those with gradable photos (n = 50,564, 96.99%), those with ungradable photos (n = 1570, 3.1%) were older, having longer diabetes duration, and worse control of glycemia (Supplementary Table 3). Thus, the estimated DR proportion in this group might be a bit higher. Finally, a total of 50,564 participants with gradable photographs were included in this study analysis.
Data collection
Information on demographics, socio-economic status, lifestyle, family history of diseases, and medical history was collected. A metabolic equivalent was calculated according to moderate- and vigorous-intensity physical activity for work, in-transit, and leisure time throughout a whole week29. After an overnight fast of at least ten hours, blood samples were collected. Fasting plasma glucose was tested in local laboratories with unified quality control. HbA1c and serum lipids were centrally measured. The blood and urine specimens were stored and then shipped at a temperature range of 2–8 °C to the Guangzhou KingMed Diagnostics Group Co., Ltd. (Guangzhou, China) for testing after the completion of the survey in one neighborhood or village26. BP, height, and weight were measured according to the standard protocol26.
Presenting visual acuity proposed by the World Health Organization (WHO) was examined30, with the logarithm of the minimal angle of resolution (log-MAR) charts used at a distance of five meters with each eye tested separately. Participants were seated in a windowless room with the lights turned off to allow the pupils to dilate naturally. Two 45-degree color fundus photographs were taken for each eye; one centered on the optic disc and the second on the macula, using a digital non-mydriatic retinal camera. The team grading the photos in this study consisted of eight ophthalmologists working in the ophthalmology department of the Shanghai Sixth People’s Hospital affiliated to Shanghai Jiao Tong University School of Medicine. All of them received standardized training before the survey. Two qualified ophthalmologists graded each photograph, and a third ophthalmologist audited inconsistent results. Masking was adopted at each stage of evaluation.
The investigation period of 488 neighborhoods or rural villages of 122 study sites across 31 provinces were presented in Supplementary Table 4.
Definition
The 31 provinces were divided into the northern or southern regions along the Qinling Mountains–Huaihe River Line31. Education levels were categorized into middle school and below as well as high school and above. Current smokers and drinkers were classified by whether they smoked or consumed alcohol during the questionnaire interview. Metabolic equivalents were calculated to express the intensity of physical activities based on the questionnaire collecting participants’ activity types and time, including work, in-transit, and leisure time in a typical week. Moderate-intensity physical activity (MET value = 4.0) was defined as a moderate amount of effort needed and noticeably accelerating the heart rate, while high-intensity physical activity (MET value = 8.0) was described as a large amount of effort required and causing rapid breathing and a substantial increase in heart rate during physical activities29. The classifications of physical activities were presented in detail in the protocol published before26. The adequate physical activity used in this study was defined as ≥600 MET minutes per week according to the Global Physical Activity Questionnaire analysis guide29. A family history of diabetes was identified if the participant answered that his or her first-degree relatives had diabetes. Metabolic control targets were defined as HbA1c < 7%, BP < 130/80 mmHg, and LDL-C < 2.6 mmol/L32.
Study-outcome definitions
The primary outcomes were the presence and severity of any DR; the secondary outcome was distant vision impairment and blindness. The presence and severity of DR were identified and graded as no apparent retinopathy, mild, moderate, and severe non-proliferative diabetic retinopathy (NPDR), and PDR33. DME was considered to be present when there was retinal thickening at or within one disc diameter of the macular center or definite hard exudates in this region34. Furthermore, clinically significant macular edema (CSME) was identified if any of the following characteristics was present: retinal thickening at or within 500 µm of the macular center; hard exudates at or within 500 µm of the macular center with adjacent retinal thickening; or retinal thickening of one disk area or greater in size, at least part of which was within one disc diameter of the macular center34. Gradings were defined according to the most severe grade of the fundus photographs in both eyes of each patient. Any DR was defined as presence of non-proliferative DR, proliferative DR, diabetic maculopathy, or a combination thereof35. Then, any DR was divided into two categories: non-VTDR and VTDR. Non-VTDR included mild and moderate non-proliferative DR, DME except CSME, or a combination thereof. VTDR was defined as presence of severe NPDR, PDR, CSME, or a combination thereof35. The distant visual impairment was categorized based on the WHO standards of blindness and vision impairment36.
Statistical analysis
Descriptive data were presented as median (25th percentile-75th percentile) for continuous variables and number (proportion) for categorical variables. Statistical analyses were performed considering strata, cluster, and weight variables to accommodate the sampling scheme unless stated otherwise. The sex-, age-, and urban/rural structure of adults with diabetes aged 18–74 years in China in 2018–2019 from the CCDRFS dataset (Supplementary Table 5) was used as a reference population for weighting frequency, and also was used to estimate 2018–2019 diabetes prevalence7. The standardized province-specific prevalence was calculated according to the sex- and age- structure of the reference using the direct standardized method.
Differences in medians or proportions between the two groups were tested using the Wilcoxon rank test or the chi-square test. The linear trend of proportions was analyzed using a logistic regression model with the median value of each subgroup representing the group level. The odds ratio (OR) and its 95% confidence interval (CI) of DR presence or severity with related factors were evaluated using the multivariable binary and multinomial logistic models, respectively. Cases with complete data on primary outcomes were used for analysis due to the small number of missing values.
Data analyses were conducted using SAS (version 9.4, SAS Institute). All tests were two-sided, and a p < 0.050 was considered statistically significant.
Data availability
The export of human-related data is governed by the Ministry of Science and Technology of China (MOST) and must adhere to the Regulations of the People’s Republic of China on Administration of Human Genetic Resources (State Council No.717). Request for the non-profit use of the dataset of the China National Diabetic Chronic Complications Study should be sent to the corresponding author Weiping Jia. The requests for the data will be replied to within 10 business days. Furthermore, the joint application for the data sharing by the corresponding author combined with the data requester should then be submitted to MOST. Upon approval from MOST, the data can be provided to the requester. The relevant data are available within the Article, Supplementary Information, or Source Data file. Source data are provided with this paper.
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Acknowledgements
We thank all investigators and all participants for their contributions to the China National Diabetic Chronic Complications Study. We are grateful for the support from the Bethune Charitable Foundation. This work was also supported by grants from the Shanghai Science and Technology Committee (grant No. 19692115900 and 17411952600), Shanghai Municipal Key Clinical Specialty, and the Chinese Academy of Engineering (grant No. 2022-XY-08) to W.J., the National Key Research and Development Program of China (grant No. 2021YFC2500201) to L.W., and the Strategic Priority Research Program of the Chinese Academy of Sciences (grant No. XDB38020000) to J.W (Jiarui Wu).
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W.J. conceived and supervised the study and provided scientific direction. D.Z. (Dalong Zhu), L.G., J.W. (Jianping Weng), Z.Z., D.Z. (Dajin Zou), Q.J., X.G., Q.W., Z.H. collected the data. M.Z., S.C., R.Y., H.C., and X.Z. performed the statistical analysis. X.H., and L.W. interpreted the results and drafted the manuscript. J.W. (Jiarui Wu) and J.W. (Jing Wu) provided critical comments and reviewed the manuscript. All authors revised the manuscript and approved the final version before submission.
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Hou, X., Wang, L., Zhu, D. et al. Prevalence of diabetic retinopathy and vision-threatening diabetic retinopathy in adults with diabetes in China. Nat Commun 14, 4296 (2023). https://doi.org/10.1038/s41467-023-39864-w
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DOI: https://doi.org/10.1038/s41467-023-39864-w
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