Epidemiology
Diabetes prevalence
The global prevalence of diabetes in 2021 was 537 million, and it is estimated to rise to 783 million by 2045.[4] In China, the country with the largest population of people with diabetes in the world, it is calculated that in 2007-2008, 92.4 million people suffered from diabetes, and 148.2 million had impaired glucose tolerance.[5] Between 1980 and 2010, the number of people in China with diabetes increased 17-fold.[6]
Retinopathy prevalence
Among individuals with diabetes, one analysis of global prevalence found that 35% have some type of diabetic retinopathy, 7% have proliferative retinopathy, 7% have macular oedema, and 10% have vision-threatening retinopathy.[7] All prevalences were greater in patients with type 1 diabetes compared with type 2, and increased with diabetes duration, poor glycaemic control, and poor blood pressure control.
In the Wisconsin Epidemiological Study of Diabetic Retinopathy, retinopathy prevalence in patients aged <30 years at the time of diagnosis of diabetes was 17% in those who had diabetes (type 1 and 2) for <5 years and 98% in those who had diabetes for >15 years.[8] Prevalence in patients aged >30 years at time of diagnosis was 29% in those who had diabetes for <5 years, and 78% in those who had diabetes >15 years.[9] A 2009 meta-analysis suggests that retinopathy prevalence may be declining. Comparing the periods 1975-1985 with 1986-2008, 4-year rates of proliferative retinopathy were estimated at 19.5% versus 2.6%, and severe visual loss at 9.7% versus 3.2%.[10]
In patients with type 1 diabetes mellitus, retinopathy is rare before puberty and rare in patients who have had diabetes for <7 years.[8] Approximately 25% of patients with type 2 diabetes have retinopathy at diagnosis, presumably as a consequence of unrecognised disease.[9]
Retinopathy incidence and progression
A review examining the incidence and progression of diabetic retinopathy in Asia, North America, sub-Saharan Africa, and the Caribbean calculated the annual incidence of retinopathy at 2.2% to 12.7% and progression at 3.4% to 12.3%.[11]
Incidence and progression rates were higher in studies carried out before 2000. The Wisconsin Epidemiological Study of Diabetic Retinopathy published data regarding 4-year incidence and progression of retinopathy in 1989. Progression from any retinopathy to proliferative retinopathy occurred in 11% of those whose age at diagnosis was <30 years, 7% of those taking insulin diagnosed at >30 years, and 2% of those not taking insulin >30 years.[12][13] In 2013, a study of patients with a similar level of retinopathy over a 4-year period showed progression rates of 0.1% to 0.5%.[14]
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