Measuring glucose levels has long been used to assess diabetes, in urine since the mid-1800s, and in blood since 1965. The current blood glucose chart classifies levels as normal, prediabetes and diabetes, a scale that also points to increasing risk of heart disease. But the scale may need a re-think.
Research has shown that blood sugar readings that fall just below prediabetes – on the higher side of “normal” – are associated with a notable increased risk of cardiovascular disease.
“Being classified as ‘normal’ is terminology that can influence perception,” said Gregg Fonarow, MD, a professor of cardiology at the David Geffen School of Medicine at UCLA. “There is a meaningful difference between those in the higher range of normal versus a lower range of normal. This hasn’t received as much attention as you would think.”
He and co-author Moein Ebrahimi, MD, reviewed two decades of research in an American Heart Journal editorial. They highlighted a 2012 study by researchers in Israel that showed double the cardiovascular risk in individuals with fasting plasma glucose readings of 95-99 mg/dL, compared with values below 80 mg/dL. A study in 2019 by researchers in Denmark and Michigan revealed that the risk was also higher with increased variability within “normal” levels of HbA1c (a three-month average of blood sugar).
To integrate these findings, Drs. Fonarow and Ebrahimi proposed a revised classification of Stages 1-4 that breaks down the normal range into lower and higher levels of glucose and associated cardiovascular risk.
Recognizing the elevated risk is the first step, Dr. Fonarow said, in “taking proactive steps to lower that risk.” That includes modifications like those undertaken during prediabetes to prevent diabetes: diet, exercise, sleep quality, a healthy body weight and medications.
Assessing risk
Cardiovascular disease accounts for 75-80% of fatalities in those with diabetes, including premature heart attacks, premature ischemic strokes, and heart failure.
Though research has established that risk of cardiovascular events can begin even with normal blood sugar levels, it’s less understood exactly why.
In studies of individuals without diabetes, high-normal glucose levels were associated with increased heart rate variability and arterial stiffness (which can lead to changes in blood pressure and blood flow).
Another possibility is glycemic variability, or fluctuations in glucose levels. The greater the fluctuations, the less the body may be able to tolerate them.
A 2021 study in Blood Pressure Monitoring connected glycemic variability with fluctuations in blood pressure in individuals with normal blood pressure. In addition, varying blood sugar levels correlate with mood disorders, a potential risk for heart disease.
In counseling his patients, Dr. Fonarow, also director of the Ahmanson-UCLA Cardiomyopathy Center, and co-director of the UCLA Health Preventative Cardiology and Cardiometabolic Health Program, explained that risk is on a gradient. For patients with normal glucose levels in the higher range, additional factors -- blood pressure readings, cholesterol and triglyceride levels, family history, age, physical activity -- must be taken into consideration.
For example, in a patient who also has borderline blood pressure, “that's going to influence us to be more aggressive with regards to managing your lipids or managing your blood pressure,” said Dr. Fonarow.
Reversing risk
Screening and awareness – what Dr. Fonarow describes as “actionable data” – allows a clinician and patient to work together to implement lifestyle modifications to reduce both blood glucose levels and associated cardiovascular risk.
“I've had a number of patients where I'm talking with them about getting 7-10,000 steps a day, improving their diet and reducing body weight,” he said. “In three months, their fasting glucose level is now improved and out of that zone of the higher range of normal.”
Digital devices can also help track progress, such as activity trackers or continuous glucose monitors, though Dr. Fonarow advised care with their use.
“Certain individuals are very data-driven and motivated and want to be able to track or get feedback on dietary changes or how they react to individual foods,” he said. “So I've had individual patients where this data has been very informative to them.”
Other health management resources at UCLA include the following:
- UCLA Barbra Streisand Women's Heart Health Program offers clinical care and outreach programs.
- The Diabetes Prevention Program (DPP), emphasizes increased physical activity and healthier food choices.
- The UCLA Fit for Health Program provides children and adolescents with guidance on healthy eating, physical activity and psychosocial wellbeing to prevent and manage overweight and obesity.
“The vast majority of cardiovascular events can be prevented,” said Dr. Fonarow, “And much of this reflects lifestyle changes and managing those risks back under the individual’s control.”
