Cardiovascular Risk Starts Even Before a Diagnosis of Prediabetes
I recently did a presentation about Insulin Resistance and the importance of early detection of Prediabetes, which is defined as a fasting plasma glucose (FPG) of 100-125 or a Hemoglobin A1c of 5.7-6.4%. Hemoglobin A1c is a lab test that gives us an estimate of the average blood sugar level over the prior 3 months.
Is Prediabetes Relevant?
I presented the research discussed below, and at the completion, an audience member asked (my paraphrase):
“I had a doctor years ago tell me that there’s no such thing as prediabetes, that there’s really no in-between…you’re either normal or you have diabetes. What do you think about that?”
It’s unclear what exactly that physician’s message was. Was her point that a) The prediabetes range is not concerning and you should only worry about being in the diabetes range, or b) Prediabetes imposes a significant risk and should be addressed with the same urgency as diabetes?
If her point was that there is no need for concern until one meets criteria for diabetes, then she is sadly mistaken. If the latter, then I fully support that notion, and I will proceed to demonstrate why. Note: I’m aware that some physicians have a hang-up over using the term “prediabetes” because not all patients with prediabetes progress to diabetes. Call it what you want…an elevated glucose is cause for concern and warrants appropriate action.
Important Perspective on Definitions of Health
First, it’s important to recognize a few truths about health:
- Health exists along a spectrum. There’s not an abrupt cutoff from healthy to unhealthy, but rather there are infinite degrees of health.
- We do not have a user’s manual for the human body. Our criteria for health and disease are merely part of a human construct to help us understand patterns of health. We don’t know what “normal” is for laboratory data; it’s simply based on an average of the general population, from individuals who are considered to be “healthy”.
- The cutoffs for diagnosis of disease processes are mostly arbitrary and may be based on consensus opinion. In fact, the National Diabetes Data Group acknowledged that “an arbitrary decision has been made as to what level justifies the diagnosis of diabetes.” The cutoff has since evolved based on the risk of diabetes-related complications.
Diagnosis of Prediabetes
As it currently stands, values greater than a hemoglobin A1c of 5.7% or fasting glucose of 100 mg/dL are sufficient for the diagnosis of prediabetes (for diabetes, these values are 6.5% and 126 mg/dL).
A large meta-analysis in 2016 looking at 53 studies with data on 1.6 million patients determined that the risk for cardiovascular disease started increasing above an A1c of 5.6% – equivalent to an average glucose of 114 mg/dL.
The A1c is felt to be a superior indicator of risk, as it better captures the cumulative exposure to sugar levels in the blood, whereas the fasting glucose offers only a very limited glimpse of the amount of sugar in the blood.
Why is a Diagnosis of Prediabetes Important?
Generally speaking, the interest in making a diagnosis of prediabetes has been to identify those at increased risk of developing diabetes. Of those who have an A1c of 5.7-6.4%, about 25% of them progress to diabetes (A1c over 6.4%) within 5 years.
However, for years, I have seen patients in my hospital practice who get hospitalized for cardiovascular disease or related events such as heart attack or stroke whose only identifiable risk factor is prediabetes. I have observed this phenomenon in adults of all ages, not just elderly patients for whom age becomes another risk factor.
A Revealing Study
It turns out that the risk of developing plaque in the arteries (atherosclerosis) – cardiovascular disease – starts even before one hits the prediabetes range. A study in Spain demonstrated that the risk of atherosclerosis starts increasing significantly in the A1c range of 5.5-5.6%, lower than the cutoff for prediabetes at 5.7%.
The importance of this finding cannot be over-stated. Let me rephrase it: People who are considered healthy in terms of their average glucose may in fact be developing cardiovascular disease without knowing it.
Our health care system does not recognize that a large percentage of people are at increased risk.
A whopping 21.2% of the study participants were in the A1c range of 5.5-5.6%. Overall, 43.8% of participants in this study were in the high-risk range of 5.5-6.4% [Note: Individuals with A1c’s over 6.4% (diabetes range) were excluded]. Also noteworthy is the finding that the A1c value was far more useful as a predictor of atherosclerosis than the fasting glucose was.
What does this finding mean for you?
If you are interested in avoiding the age-related diseases plaguing our population, then you need to aggressively pursue optimal health. “Normal” is not good enough.
The individuals in the above-mentioned study who had hemoglobin A1c’s of 5.5% were considered to be “low risk” for heart disease. They actually had significant disease that just wasn’t symptomatic yet.
You must be proactive about your health, because our current system of health care does not recognize anything wrong with an A1c less than 5.7%, even though these data indicate otherwise. With the current low bar for health care in this country, there will be no effort made to address this unappreciated risk and certainly no effort to optimize your metabolic health.