How Low Should You Go
The perspective of an eye doctor with diabetes
Ever since completion of the Diabetes Control and Complications Trial (DCCT) in patients with type 1 diabetes, and the United Kingdom Prospective Diabetes Study (UKPDS) in patients with type 2 diabetes, most doctors and other health care professionals have recommended that people with diabetes try to keep their blood glucose levels as close to normal as possible. After all, both the DCCT and the UKPDS showed that tighter blood glucose control, as reflected by glycosylated hemoglobin (HbA1c), greatly reduces the risk and progression of specific diabetes complications: retinopathy (eye disease), nephropathy (kidney disease) and neuropathy (nerve disease).
Consequently, the American Diabetes Association recommends HbA1c levels less than 7%, while the American Association of Clinical Endocrinologists recommends even tighter control, with HbA1c levels less than 6.5% for "most patients." People excluded from these recommendations include children (for whom increased hypoglycemia may pose risks to brain development) and patients with certain forms of heart disease (whom also have been thought to be at higher risk for worsening of their condition if blood sugar levels become too low). It is important to note, however, that no clinical studies had shown that these groups should be ‘excused' from tight control – the ratio of risk to benefit was simply assumed to be too high.
More recently, three large studies have examined whether or not people with type 2 diabetes and preexisting cardiovascular disease or multiple risk factors for it might benefit from tighter blood glucose control. The first study to be published, ACCORD, actually showed that patients who attempted tighter control had a 22% increased risk of dying. The second study, ADVANCE, showed no increased or decreased risk of cardiovascular events or death, but a decreased risk of kidney disease. The third, on-going study of US veterans, VADT, again showed no increased or decreased risks of major events (like heart attack) or death even though these patients had, in general, poorer diabetes control and heart health than patients in ACCORD and ADVANCE. The results of these studies are still being analyzed and hotly debated, but it appears we can safely say that tighter blood glucose control, with currently used medications and lifestyle modifications (i.e. diet and exercise recommendations) does not improve cardiovascular outcomes for patients with high cardiovascular risk.
Unfortunately, many in the media seized upon the results of the first trial, ACCORD, reporting that tighter glucose control is a bad idea for patients with high cardiovascular risk, ignoring or down playing findings of the other two studies. Additionally, because critical distinctions in clinical research are harder for lay persons to fully appreciate, they often get lost or obscured by news media, and there were some reports that tight blood sugar control is a bad idea in general. Subsequently, I have had a number of patients, both with and without heart disease, question my advice to keep their blood glucose levels well-controlled to prevent vision loss from diabetes.
This alarms me, because tight blood sugar control, along with tight blood pressure control and regular dilated eye exams, is one of the most important strategies for preventing vision loss and blindness caused by diabetic retinopathy, the leading cause of blindness in working age Americans – the DCCT proved it, the UKPDS proved it, a number of other studies have proven it. In fact, each 10% reduction in HbA1c (for example, lowering the value from 7% to 6.3%) reduces the risk of diabetic retinopathy getting worse by more than 40%.
From my perspective as a patient who has had diabetes for forty years, as someone who nearly lost his vision to diabetes 23 years ago, and as an eye doctor who sees patients every day with diabetic retinopathy - the majority of whom have poor blood glucose control and don't fully understand its importance - it is critical that we not throw the baby out with the bath water. Tight blood glucose control saves vision. It is a great idea for patients who are not at high cardiovascular risk, and may very well benefit the eyes, kidneys, and nerves of patients who are at high cardiovascular risk. For the latter group only, it may or may not be good for the heart (though I suspect future evidence may point to survival factors not accounted for by ACCORD, ADVANCE or VADT – such as total carbohydrate intake and blood levels of insulin), but we should have no doubt that it will preserve eyesight. Reporting of these studies also underscores the need for all of us involved in diabetes care, both providers and well-informed patients, to redouble our efforts at getting the word out about the overall importance of optimizing blood sugar control and consulting our doctors when the newest research hits the popular media.
For more information on diabetic eye disease, consult Dr. Chous' book Diabetic Eye Disease: Lessons From a Diabetic Eye Doctor, Fairwood Press, Seattle, 2003.
Read more about Dr. Chous here.
Visit Dr. Chous' website here.
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.
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