The Nutrition Debate #241: “HbA1c Increases with Age”

The headline in Diabetes in Control reads “HbA1c Increases with Age.” Headlines like this are often evidence of confirmation bias and are perilously misleading to the uninitiated. So, I had to read the digest piece and then the abstract in the medical journal Diabetic Medicine. If you register and pay a $$$ fee, you can get 24-hour online access to the full study from publisher Wiley.com. Such is the cost to society of dissemination of partially government-funded medical research.

Interestingly, at first glance, only the digest is guilty of confirmation bias. The medical journal is just guilty of myopia. I say “at first glance” because that is the only look I can afford. The full study could disabuse me of my take (and my biases). That said, this study was a review of two-large datasets. The aim was “to determine whether using HbA1c for screening and management, in a “cross-sectional analysis in adults without known diabetes,” the effects of aging have an impact on diagnostic accuracy.” That’s a reasonable AIM, and the researchers produced some interesting, but unsurprising RESULTS.

My quarrel, therefore, is not with the researchers. It is with Diabetes in Control, and primarily with their headline writer in particular. It is not nit picking to point out that the headline and the story in Diabetes in Control are contradictory. Neither is the headline consistent with the AIM, RESULTS or CONCLUSION of the scientific paper, as reflected in the ABSTRACT. In addition, disparities like this just cause me to get a bit unglued and go off on a rant, so hold onto your seat. It’s a brief one.

The study adjusted for covariates for a multitude of factors, such as race, BMI, etc, but not for treatment modality. Here’s where the myopism, or maybe just ignorance comes in. Everyone in both datasets received the same or similar failed treatment plan that is the ADA Standard of Care of type 2 diabetes. So, naturally, everyone’s A1c increased as they got older! BREAKING NEWS: It was supposed to increase as they got older! The current medical definition of diabetes is that it is a progressive disease. That means: Your condition will get worse as you get older IF YOUR DOCTOR FOLLOWS THE ADA STANDARD OF CARE. And guess what, as your condition gets worse, your A1c will get worse. How could it be otherwise?!!!

So, that’s where the digest failed. It just saw this result the way it was predisposed to see it. Except it was also careless; it describes the datasets as “adults with known diabetes.” Maybe it was just a typo. But my editor would have caught it (LOL).

Another quibble I have is with the characterization that “the researchers found a remarkable decrement in the performance of the predictive value of A1c as compared with a 2-hour Oral Glucose Tolerance Test (OGTT), with age. Well, la dee dah. It shouldn’t come as news that the OGTT is and will always be the “gold standard” for screening for type 2 diabetes. I had one in the 1980s. Have you ever had one? Do you know anyone at all who ever has?

But my quibble is not with the obvious superiority of the OGTT; it is with the term “remarkable decrement.” The Abstract provides some specificity. In elderly subjects without diabetes, over 10 years, their HbA1c’s increased less that 1/10^th of one percent, whereas in an analysis of all elderly subjects, including those with diabetes on that failed treatment modality, their HbA1c increased by less than 1%. For reference, remember that the A1c Standard of Care for the general population of type 2 diabetics is 7%, but in the elderly the ADA now sets the bar as high as 9% to “lessen the burden” on the patient. In reality, it’s recognition and concealment by subterfuge of a failed medical policy.

Of course, the RESULT is that, when treated to the ADA Standard of Care, as all the patients in both large subsets of data presumably were, “both glucose tolerance and HbA1c levels increased with age.” I guess that’s what the Diabetes in Control headline writer saw first, and used to confirm their bias.

Another result was stated thus: “The HbA1c of an 80-year old individual with normal glucose tolerance would be 0.35% greater than that of a 30-year old with normal glucose tolerance, a difference that is clinically significant.”

Another: “The specificity of HbA1c-based diagnosis criteria for prediabetes decreased substantially with increasing age.”

Okay. One of the Diabetes in Control conclusions: “Age should be taken into consideration when using HbA1c for the diagnosis and management of diabetes and prediabetes.” Fair enough.

My conclusion: Everyone, who on the basis of 2 consecutive elevated Fasting Blood Glucose tests, or whose HbA1c is 5.7 or higher and is therefore suspected of prediabetes or type 2 diabetes, should have a 2-hour Oral Glucose Tolerance Test.

Can’t get one? Check your post prandial glucose readings.