Original articleIncidence and progression of diabetic retinopathy in Hong Kong Chinese with type 2 diabetes mellitus
Introduction
Diabetic retinopathy (DR) is an important and common microvascular complication of diabetes mellitus. It is the most frequent cause of blindness among adults aged 20–74 years in the United States. The Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) showed that 1.6% of type 2 diabetic patients were legally blind (Centers for Disease Control and Prevention, 1996). Up to 21% of patients with type 2 diabetes have DR at the time of diagnosis of diabetes. Nearly all patients with type 1 diabetes and >60% of patients with type 2 diabetes had DR after 20 years of diagnosis (American Diabetes Association, 2004). Type 2 diabetes has reached epidemic proportions in the Asia-Pacific region. It was estimated that 9.8% of Hong Kong Chinese had type 2 diabetes in the year 2000 (Cockram, 2000). The increasing number of type 2 diabetics means that DR will continue to pose a major problem.
The incidence and progression of DR in Caucasians and other populations have been demonstrated in a number of studies. However, published data on the incidence and progression of DR in the Chinese population are limited. We performed a cohort study to evaluate the incidence and progression of DR over 4 years in a Chinese population with type 2 diabetes in a district hospital in Hong Kong, and to identify the risk factors associated with the development and progression of DR. By finding the potential predictors of DR, we can identify at-risk patients so that appropriate intervention can be implemented.
Section snippets
Subjects
All type 2 diabetic patients of Chinese ethnicity who followed up in the diabetic clinic of the Caritas Medical Center and had a diabetic complication screening performed in the year 2001 were recruited in the study. The baseline examination included 413 subjects, and the baseline prevalence of DR was estimated.
They were regularly followed up by physicians in our diabetic clinic every 4–16 weeks. On each visit, blood pressure and body weight were recorded. Fasting glucose and HbA1c were
Baseline characteristics of subjects
The baseline demographic and biochemical parameters of the 413 subjects are shown in Table 2. There were more female (59.6%) than male subjects (40.4%). The mean age was 55.2±9.5 years (range, 20–77 years). The mean duration of diabetes was 8.8±6.1 years (range, 0–41 years), and the mean baseline HbA1c was 8.1±1.5%. Most patients (71.4%) were treated with oral hypoglycemic agents alone. Hypertension was present in 251 (60.8%) patients.
Baseline prevalence of DR and risk factors associated with DR
At baseline, DR was present in 162 of 413 patients, giving a
Discussion
The prevalence of DR in Hong Kong Chinese in our study was 39.2% in 2001. The prevalence of DR in this study was similar to those of the UK Prospective Diabetes Study (UKPDS; 37%) (Stratton et al., 2001) and the Melbourne Visual Impairment Project (35.7%) (Dimitrov, Mukesh, McCarty, & Taylor, 2003), but higher than that of the Pima Indians study (31.8%) (Looker et al., 2003). The lower prevalence of DR in Pima Indians might be attributed to their diabetes screening program in which regular
Conclusion
DR is prevalent in Hong Kong Chinese with type 2 diabetes. Our study showed that the incidence of DR was comparable to—but progression was higher than—that in Caucasians. Regular screening is necessary for early detection and treatment. Poor glycemic control is strongly associated with the development of any level of DR. Once retinopathy has been established, both poor glycemic control and presence of macroalbuminuria predict its progression. Hence, more frequent retinopathy screening should be
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