The Importance of Achieving Tight Control of Blood Sugar
Study finds diligence saves vision
By A.Paul Chous, MA, OD, FAAO
A recent report based on findings from the famous Diabetes Control and Complications Trial (DCCT) and its companion study, the Epidemiology of Diabetes Interventions and Complications trial (EDIC) has highlighted the importance of achieving tight blood sugar control soon after being diagnosed with diabetes. The DCCT followed patients with type 1 diabetes for 10 years and showed that achieving near normal blood sugar control, as reflected by an average hemoglobin A1c result of 7.2% (equivalent to an average blood glucose level of about 175 mg/dl), dramatically reduced the risk of small blood vessel diabetes complications by the end of the study – especially diabetic retinopathy – when compared to poorer blood sugar control (average hemoglobin A1c of 9%, equivalent to an average blood glucose level of about 245 mg/dl).
The EDIC study followed patients from the DCCT for an additional decade and showed that this reduction in risk for small blood vessel complications persists over time, even though average blood sugar control in both of the original groups became nearly identical over time (patients in the tight control group developed worse blood sugar control and patients in the poor control group developed better blood sugar control over time, with an average A1c of about 8% by the end of the 10 years for both groups). Based on these findings, the EDIC study suggests that there is a delayed, protective effect conferred by achieving tight blood sugar control early on, what is often referred to as protective "metabolic memory."
The authors of the recently published paper, appearing in the journal Archives of Internal Medicine, continued to follow the same group of patients from the DCCT and EDIC studies for an additional 10 years and found that after nearly 30 years, less than 1% of patients in the original, more tightly controlled group had suffered blindness, end-stage renal disease (kidney failure requiring transplant) or lower limb amputation. These incredibly positive findings with respect to vision loss and diabetes are also due to great advances that have been made in treating eye disease, but it is also true that preventing eye disease and its progression (worsening) in the first place, by controlling our blood glucoses early on, will literally save vision. For eye doctors and our patients, what this means is that we need to work together with endocrinologists and primary care physicians to get tight control of diabetes as soon as possible after diagnosis. As it turns out, letting blood sugar levels remain out of control for even a few years after diagnosis may make a tremendous difference in both the need for treatment and bad outcomes like impaired vision or even blindness.
How about for the majority of patients with type 2 diabetes? Does early, good control also make such a big difference? Recent results from a follow-up to the United Kingdom Prospective Diabetes Study (UKPDS) suggest that it does. The original UKPDS showed that, among other things, tight control of blood glucose significantly reduces the risk of eye disease in T2DM, whereas follow-up of these same patients reveals a 24% reduced risk for diabetic retinopathy even though blood sugar control worsened over time, as it did in the DCCT. Again, the common thread amongst these studies is that getting good control of our blood sugars as quickly as possible may be of paramount importance.
I know, getting diagnosed with diabetes is a big shock, and it can take months or even years to figure out how to manage diabetes well – but, for those of us who don't want complications – and I have no doubt that's every single one of us – we simply can't afford that much time. In my view, that is why it is imperative not only to prevent diabetes, but to develop a first-rate, national system of diabetes care and education that empowers every person who is diagnosed to take control of his or her diabetes ‘right out the gate.' More on this next time.
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NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
1- Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) Research Group, Nathan DM, Zinman B, Cleary PA, Backlund JY, Genuth S, Miller R, Orchard TJ. Modern-day clinical course of type 1 diabetes mellitus after 30 years' duration: the diabetes control and complications trial/epidemiology of diabetes interventions and complications and Pittsburgh epidemiology of diabetes complications experience (1983-2005). Arch Intern Med 2009 Jul 27;169(14):1307-16.
2 - White NH, Sun W, Cleary PA, Danis RP, Davis MD, Hainsworth DP, Hubbard LD, Lachin JM, Nathan DM. Prolonged effect of intensive therapy on the risk of retinopathy complications in patients with type 1 diabetes mellitus: 10 years after the Diabetes Control and Complications Trial. Arch Ophthalmol. 2008 Dec;126(12):1707-15.
3 - Holman RR, Paul SK, Bethel MA, Matthews DR, Neil HA. 10-year follow-up of intensive glucose control in type 2 diabetes. N Engl J Med. 2008 Oct 9;359(15):1577-89. Epub 2008 Sep 10.
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