Retrospective #362:A Stricter Prediabetes Definition

In 2016 a Reuters Health Information article in Medscape Medical News headlined, “Meta-Analysis Backs Stricter Prediabetes Definition.” It reports on a new study in the BMJ (British Medical Journal) that “people with a fasting glucose as low as 100mg/dl (5.6mmol/L) are at increased risk of cardiovascular disease.” It also showed increased CVD risk in individuals with an HbA1c as low as 5.7% (39 mmol/mol). What is significant about this Chinese study is that it is very large (53 studies, comprising 1,611,339 people). The big takeaway: “Effective intervention in prediabetes is not just for prevention of diabetes, but also cardiovascular diseases.”

This isn’t news to my regular readers. I have been saying it forever, most recently in the risk analysis presented in Retrospective #345, “How Diabetic Do You Want to Be? (Part 2). That column was based on the laudatory work of Jenny Ruhl at her website, Blood Sugar 101. Jenny has meticulously collected and provided links to the best research. Her books, “Blood Sugar 101” and “Diet 101,” are awesome too.

Based on the ADA criteria for an Impaired Fasting Glucose (IFG) of 100mg/dl to 125mg/dl (5.6 to 6.9mmol/L), the study found that the association between prediabetes and various co-morbidities is as follows: CVD ↑ 13%; CHD ↑ 10%; Stroke ↑ 6% and All-Cause Mortality ↑ 13%. But the ADA criteria is “contentious,” the authors told Medscape, and “has not been used in other international diabetes management guidelines.” The WHO (World Health Organization), for example, uses a higher cutoff for diagnosing an Impaired Fasting Glucose, 6.1 to 6.9mmol/L (110-125mg/dl), and thus has a higher hazard ratio for “composite cardiovascular disease” of ↑26%.

Similarly, the ADA’s prediabetes criteria for an HbA1c is 39-47mmol/mol (5.7% -- 6.4%), whereas the National Institute for Health and Care Excellence (NICE at Braiain’s NHS) cutoff, 42-47mmol/mol (6.0% -- 6.4%), is different. As a result, CVD relative risks vary from 13% (IFG-ADA) to 26% (IFG-WHO), relative risks for CHD vary from 10% to 18%, and relative risks for stroke vary from 6% to 17%. The authors also argue for the standardization of IFG and IGT (Impaired Glucose Tolerance), and the worldwide incorporation of HbA1c in defining prediabetes.

 But let’s not get lost in the weeds. The bottom line is this: The current cutoffs worldwide for a diagnosis of prediabetes are strongly associated with an increased risk of CVD, CHD, stroke and all-cause mortality. This is in addition to the usual microvascular complications of T2DM of nephropathy (end-stage kidney disease), retinopathy (blindness), and neuropathy (leading to amputations). There is also a similar pattern for dementia (Alzheimer’s).

That’s the message, and that is why I am pleased to see this hue and cry for a stricter and more standardized prediabetes definition. The medical doctor’s response was predictable: “People with diabetes should be followed up and should maintain a healthy lifestyle” (emphasis added by me). And “many drugs prescribed for diabetes may be useful in people with prediabetes (e.g., metformin, acarbose).” The latter is also not news, but it is surprising how many doctors don’t know this and do not routinely employ this intervention in clinical practice.

Then, according to Medscape, the study’s lead author, a research physician, suggests that, “First, we need to develop models for risk stratification in people with prediabetes. Second, we will select higher-risk people with prediabetes to evaluate whether drug treatment can prevent cardiovascular disease in them.” Not a word about diet.

I’m not surprised by this either. Drugs, drugs, drugs. Always treat the symptom (an elevated blood sugar); never treat the cause (Insulin Resistance → Carbohydrate Intolerance). What about “lifestyle modifications” (diet)?

Lifestyle modifications address modifiable risk factors. That means you can do something to reduce your increased risk of cardiovascular disease. You can modify your diet by restricting the amount of carbohydrates you eat and thus lower your blood sugar without drugs. Jenny Ruhl #1: ↓Dietary Carbohydrates = ↓Insulin Resistance = ↓Type 2 Diabetes.