Diabetes NewsJuly 2009
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Timing is Everything in the Risk of Retinopathy
Diabetes Care • October, 2008
Over the past ten years we have seen a nearly doubling of the rate of new cases of diabetes in our country according to the Center for Disease Control (CDC). Roughly ninety percent of the cases are Type 2 diabetes which researchers link to obesity. These findings support the trends seen with the increase in obesity and lack of exercise over that time period. More than 23 million Americans have diabetes and the number is rapidly growing with about 1.6 million new cases diagnosed last year. The CDC also reports that diabetes was our nation’s seventh leading cause of death in 2006.
We are currently facing a worldwide epidemic onset of diabetes which knows no age boundaries nor geographic borders. Evident in this trend is an ever decreasing age of the diagnosis of Type 2 diabetes. Recent studies reveal that Type 2 diabetes constitutes up to 45% of incident pediatric diabetes, and 7-22% of adolescent diabetes presents with diabetes-specific complications at diagnosis.
To date few studies have examined long-term outcomes as a function of age of diagnosis in type 2 diabetes, and even fewer have looked at the development of retinopathy specifically. There is some limited data suggesting that young-onset diabetes is associated with increased risk for complications compared with later-onset disease and that the development and progression of complications might be particularly rapid in early-onset disease. What is hereto unknown is whether the increased prevalence of complications associated with early-onset diabetes is simply a consequence of longer duration of the disease, or a more severe metabolic phenotype, or in fact something specific to the diabetic milieu in younger patients that makes tissues more inherently susceptible to hyperglycemic damage.
Researchers at the Diabetes Centre, Royal Prince Alfred Hospital in Sydney explored the hypothesis that in type 2 diabetes, susceptibility to retinopathy is dependant upon age of diabetes onset. The isolated effect of age of diabetes onset on long-term retinopathy status was examined independent of duration of diabetes and glycemic control, the two most important risk factors for developing retinopathy.
Objective - Researchers at the Diabetes Centre, Royal Prince Alfred Hospital looked to see if the age of onset of Type 2 diabetes influenced the inherent susceptibility to diabetic retinopathy independent of other factors.
Research Design and Methods - Researchers gathered retinopathy data from 624 patients with Type 2 diabetes of duration 20 to 30 years (Group A) and were analyzed according to age of onset and blood sugar control. To remove possible bias from the study due to a higher attrition from comorbidities in those with later onset of retinopathy, 852 patients (Group B) with type 2 diabetes of shorter duration were similarly studied. Retinopathy status was scored clinically as per a modified Early Treatment Diabetic Retinopathy Study (ETDRS) severity scale.
Results - Prevalence and severity of retinopathy was significantly higher in the younger-onset, Group A patients. When further stratified according to mean A1C, retinopathy risk remained increased with younger-onset patients. The greatest impact was seen in those with a mean A1C >9%, the odds ratio for development was 16.6 for onset age less than 45 years, 7.5 for onset between ages 45-55 and 2.7 for onset age after 55 years. Similar results were found in Group B.
Conclusion - These data suggest an increased inherent susceptibility to diabetic retinopathy with earlier-onset type 2 diabetes. This further supports the importance of delaying development of diabetes and also implies a need for more stringent metabolic targets for younger individuals.
Reprinted with permission from the American Diabetes Association