HbA1c: Biomarker of Health

Photo by Sam Azgor.

This post is part of a series on 

Biomarkers of Longevity & Health

Because I have have several members in my extended family who are diabetic (both Type I and Type II), I tend to read more about diabetes for someone without a diagnosis. 

I want to offer diabetic family members support.

I also want to understand the risks that my children and I might face because of the history of diabetes on my side of the family.

Most recently, I have been interested in learning more about the HbA1c test, also called the A1c test.

I'm invested since increased control of blood sugars correlates with greater longevity and health.    

People with poorly managed blood sugar levels have increased risk for a number of health problems, notably the following:

• Eye disease
• Heart disease
• Kidney disease
• Nerve damage
• Stroke 

Emerging research published in the New York Times in 2013 suggest those with poorly maintained blood sugar are also at risk for dementia due to Alzheimer's Disease and vascular disease.   Neurology Advisor summarizes a 2015 Swedish study of 350,000 people (average age 67) with Type 2 diabetes and found this correlation: 

"After taking other variables into account, the researchers found that those with HbA1c levels of 10.5% or higher were 50% more likely to be diagnosed with dementia than were people with HbA1c levels of 6.5% or less."

What does HbA1c measure? 

Many diabetics test their blood at home in an an effort to keep their blood sugars within a healthy range, typically identified as 80 to 120 milligrams per deciliter (mg/dL).   

[Please see a licensed health care professional in order to maintain good health. This post is only for raising awareness and should not be a substitute for professional medical advice.]

Blood glucose measurement provides only a snap shot of glucose levels at a specific moment in time, a level that may exist for mere minutes.  

The HbA1c test offers a window into the rate of glucose in the blood over several weeks. The test scores differ because they measure different things. An HbA1c score is in a percentage, and might be somewhere between 5% and 10%. 

More on HbA1c results below, but know that lower numbers are ideal, but not numbers lower than 4%; that suggests problems with too frequent hypoglycemia.

Because HbA1c tests phenomena occurring over several weeks, it offers a fuller picture than home blood glucose monitoring.

HbA1c measures the percentage of hemoglobin that have glucose attached to them. When this happens, the result is termed glycated hemoglobin. If a person has many instances over several weeks of hyperglycemia (high blood sugar levels), their percent of glycated hemoglobin will be higher.

I found over a dozen videos explaining HbA1c, and I like this one the best.  For starters, it is not connected with a testing service, which might exaggerate the convenience and usefulness of the test. 

This video also does a good job of explaining the time frame of the HbA1c test.

Although the life cycle of an individual hemoglobin is 120 days, the the average life of the blood's massive collection of hemoglobin taken in a blood test must be lower since they are continually entering and exiting the blood system. The test results, therefore, measure the average life of the blood's hemoglobin at the time of the draw. And that average would be closer to 60 days. 

What is an ideal test result for HbA1c?

I have seen some variation in ideal ranges.  

The most consistent number I've seen is 6.5% as the threshold for diagnosing a person with diabetes.  A person without a diagnosis of diabetes usually has test results between 4% and 6%. 

The ideal test result may vary--5%, 6% or even 7%--depending on the individual's age and condition. It's important to work closely with a medical professional (for example, a physician's assistant, general practitioner, internist or endocrinologist) to determine a target test result.   

Many sources emphasize that lowering a score by even 1% has great benefits, even if that improved number is still above 6.5%.

For example, if a person had been testing quarterly for five years at 8% HbA1c and finally maintained a result of 7% over a year of quarterly tests, that would be a triumph.  

Here is a chart for an individual sharing HbA1c test results over several years. (Click on image to enlarge.)

Photo by E.S. O'Connor. Click to enlarge or follow link. 

And kudos to Erin (the patient whose results are displayed above) for staying "in the green" for so many tests. 

Do you want to read more about HbA1c?

If you want to read extensively about HbA1c, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) has an outstanding page here. 

Here is a 2013 study of 933 Japanese centenarians that shows A1c levels below 6.0.  See Table 1 for specifics.  

Here is a MedPage Today 2012 article citing studies about the increased risk of microvascular disease correlated with elevated HbA1c levels.

Related:

Biomarkers for Longevity and Health