Low prevalence of diabetic retinopathy in a Chinese population.

As a typical microvascular complication and a leading cause of blindness in working-age individuals, diabetic retinopathy (DR) is a serious threat to the quality of life for millions worldwide. The prevalence of diabetic retinopathy is 22–37% in individuals with known diabetes (1,2) and 6–13% in individuals with newly diagnosed diabetes (3). However, current estimates of the prevalence and risk factors for DR are mostly derived from studies of Western populations. Population-based data on DR in Asians remain limited.

It has been hypothesized that ethnic differences may result in varying susceptibilities to diabetic microvascular complications (4). For example, Greek ethnicity may confer some protection against DR (5).

From July 2010 through March 2011, the 2010 Health Examination Survey in Beijing, a population-based survey on chronic diseases and risk factors, was conducted in Changping, one of the newly developing districts in Beijing. In a total of 8,155 Chinese between 18–79 years of age, representing a population of 1,660,500 in the district, 3,760 subjects had a fasting plasma glucose ≥5.6 mmol/L. Of these, 2,592 subjects (68.9%) consented to participate in the study. After excluding 31 subjects with cataracts and 10 with other eye diseases, 2,551 individuals completed the biochemical and ophthalmic examination. Two 45° color digital images of the retina, centered at the optic disc and macula, were obtained from both eyes of each participant using a Topcon TRC-NW7SF fundus digital imaging system.

Of the 2,551 individuals (1,229 male and 1,322 female, with an average age of 48.8 ± 12.1 years), 280 with known diabetes, 334 with newly diagnosed diabetes, and 853 with impaired glucose regulation were identified. The prevalence of DR in diabetic and impaired glucose regulation subjects was 9.9 and 1.2%, respectively. The known diabetic subjects had the highest frequency of DR (18.6%), which was 2.7% in the group with newly diagnosed diabetes. According to retinopathy grades, the frequency of mild nonproliferative retinopathy (NPDR) and moderate NPDR in known diabetic subjects was 8.6 and 8.2%, respectively, whereas severe NPDR and proliferative retinopathy in known diabetic subjects were rare (3 and 2 cases, respectively). Three cases were found with DR in 1,084 normal glucose tolerance subjects. In diabetic patients, independent risk factors for DR were longer diabetes duration (odds ratio 1.49 [95% CI 1.38–1.62], per year), plasma glucose levels during the oral glucose tolerance test (1.32 [1.22–1.43] and 1.18 [1.12–1.24], per mmol/L for 0 h and 2 h, respectively), HbA1c (1.66 [1.45–1.90], per 1%), and higher systolic blood pressure (1.16 [1.02–1.31], per 10 mmHg).

The current study provides new data on the epidemiological characteristics of DR in a population-based sample of Chinese adults. The prevalence of DR in persons with diabetes was lower than that reported in Western countries. The major risk factors for DR are a longer duration of diabetes, poor glycemic control, and hypertension. The low prevalence of DR in Chinese patients with diabetes and prediabetes raises the question of the clinical significance and the economical effectiveness of regular DR screening.