Hemoglobin A1c: Is Lower Always Better?

First, I must apologize once again for such a long time between entries.  My only excuse is that I have been very busy with other things.  I will try to post at least one entry a week, at least that is my goal.

The other day, a friend asked my advice about her father’s diabetes.  He is 84 years old and has type 2 diabetes.  For the past few years he has been insulin-dependent.  He had been doing poorly with his diabetes, but over the past few months with the help of friends and family members, had gotten much more on track- better eating habits, more blood glucose testing, fewer missed insulin injections, etc.  He had been prescribed insulin glargine (Lantus brand) at bedtime and insulin lispro (Humalog brand) before meals.  Three months ago, his blood glucose levels were consistently high and his HbA1c was 9.8 % (normal range is about 4%-6%).  But, last week, his HbA1c was 7.4% and blood glucose checks were mostly in range, with no hypoglycemia.  His family physician was very pleased with his progress, but felt it would be worth “pushing” harder for a lower HbA1c (less than 7%), and prescribed dulaglutide (Trulicity brand), a glucagon-like peptide-1 agonist, in addition to the insulin.  My friend, wisely “googled” the medication and learned that it was used to treat some patients with type 2 diabetes, those who still had some pancreas insulin production.  My friend was reluctant for her father to add another medication to his diabetes care regimen, particularly given how well her elderly father had been doing recently.  She read that the Trulicity could cause hypoglycemia and gastrointestinal upset.  She asked me what I thought.  I told her that given her father’s age, recent data had shown that “pushing” for the best possible HbA1c was not always the best thing for a patient with diabetes, and I agreed with her concern.  You can imagine my amazement when what should come along the day after I talked with my friend, but a NYT article that addressed the very issue we had been discussing.  The article was entitled: “A diabetes dilemma,” written by Gina Kolata (NYT June 6, 2017, page D5).  I strongly recommend that you read the article, especially if you are a health care provider who cares for people with diabetes ( or have an elderly parent with type 2 diabetes).

Historical Perspective

First, I confess that just about everything I am going to discuss in this entry, I have addressed in earlier entries, but I have never discussed HbA1c from this perspective.  When the now famous Diabetes Control and Complications  Trial (DCCT) initial results were announced in 1993, a revolution in diabetes care was launched .  The DCCT proved for the first time in convincing fashion that glycemic control (as assessed by serial HbA1c determinations) was a strong predictor of diabetes complications.  Almost immediately, the American Diabetes Association ADA) proposed diabetes treatment goals based on HbA1c levels: for most people with diabetes, the goal should be HbA1c of 7% or less.    The ADA also proposed an “action needed HbA1c level” of 8% or greater.  These recommended treatment goals were subsequently modified by pressure from some diabetes clinicians, to eliminate the “action needed goal,” and focus on a single goal of 7% or lower (some suggested the goals should be 6.5% or lower).  In all the excitement, most diabetes health professionals did not fully understand what the DCCT results had taught us about the relationship between HbA1c level and risk for diabetes complications.  The  HbA1c vs. risk curves for the various diabetes complications were not linear, but rather, they were curvilinear.  What this means is that improving HbA1c from 9% to 8% carries a much greater risk reduction than improving HbA1c from 8 to 7%; improving the HbA1c from 7%  to 6 % barely lowers the risk.  We also knew that the lower the HbA1c, the greater the risk for serious hypoglycemia.  For a young child or an elderly person, the health benefit of lowering the A1c to 7% or less, might not be worth the risks involved.  As the NYT article points out, recent studies have shown that “pushing” to achieve a near-normal HbA1c is associated with increased deaths, not fewer; the theory is that the excess deaths in the low HbA1c patients is caused by cardiovascular disease triggered by hypoglycemia.  Whether this is the mechanism for the increased death rates in diabetes patients with very low HbA1c levels remains to be proved.  But, if there is no significant health benefit in dropping the HbA1c to some arbitrary meritorious level, we should think twice about HbA1c treatment goals.  We must also remember that pushing for near-normal HbA1c levels may be a problem with a compulsive patient, not an overzealous health professional.  We need to make certain that all patients with diabetes, regardless of whether it is type I or type 2, understand that HbA1c is a very important diabetes treatment tool, but that like any tool, it is important to know how to use it properly.

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