October 24, 2011 — A 20-year observational study has chronicled notable declines in retinopathy for young patients with type 1 diabetes who receive intensive glycemic control therapy, confirming earlier findings that found a link between normalized blood glucose levels and the slower progression of eye, kidney, and nerve damage.
A review of 1604 adolescents and teenagers stratified into 4 periods between 1990 and 2009 and evaluated for contributors to diabetes-related complications showed that retinopathy frequency dropped when glucose control therapy went beyond the standard regimen of 1 to 2 insulin injections/day. Researchers associated steady decreases in the onset of retinopathy over time with increasing percentages of study participants who were subjected to multiple daily injections (MDI; 3 or more injections daily) or continuous subcutaneous insulin infusion (CSII).
Results of the study, coordinated by physicians associated with the Institute of Endocrinology and Diabetes at the Children's Hospital in Westmead, Australia, are being published by the American Diabetes Association in the November issue of Diabetes Care.
Study participants (54% girls) ranged in age from 12 to 20 years and had a mean 8.6-year duration of type 1 diabetes. Physicians performed 2030 assessments of complex risk factor profiles associated with various type 1 morbidities, and were able to correlate the use of stricter glycemic control therapies with reduced incidence of retinopathy throughout the entire observational period.
Prevalence of retinopathy dropped from 53% of 342 patients assessed between 1990 and 1994 to 38% of 517 patients assessed between 1995 and 1999. Incidence continued to decline in subsequent time-stratified groups, with a 23% prevalence recorded for 604 patients assessed between 2000 and 2004 and a 12% retinopathy prevalence demonstrated in 567 patients evaluated between 2005 and 2009 (P < .001).
Only 17% of the 1990 to 1994 patient population, which showed the highest frequency of onset, were subjected to the more rigorous MDI or CSII techniques. In contrast, the 2005 to 2009 patient group, which exhibited the lowest retinopathy prevalence, had the highest level of adherence (88%) to MDA/CSII therapies.
"There was some evidence that there was a reduced risk of retinopathy in those treated with CSII versus MDI," the authors write. "[H]owever, this did not reach statistical significance (p=0.07)."
No increase in risk for severe hypoglycemia was associated with glucose management control adjustments.
The Australian study builds on earlier research conducted to quantify normal glycemic targets that are recommended for healthy function, and specifically those elucidated in the Diabetes Control and Complications Trial of 1983 to 1993. That study, conducted in 29 American and Canadian medical centers, enrolled 1441 patients aged 13 to 39 years with type 1 diabetes durations as short as 1 year.
The Diabetes Control and Complications Trial concluded that intensified blood glucose control techniques that keep A1C levels as close as possible to normal levels could help reduce vision morbidity risk by 76%.
In the more recent study, researchers acknowledged the potential for a response bias resulting from the inclusion of more than 1 visit for some patients across different periods. However, they pointed out, no difference in response trends over time was noted when only 1 assessment per patient was analyzed.
The authors have disclosed no relevant financial relationships.
Diabetes Care. 2011;34:2368-2373. Abstract
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