Heart disease: High blood sugar below diabetes threshold raises risk

Researchers analyzed data from the UK Biobank of more than 427,000 UK residents for the study.

About 54% of participants were females and about 46% were males. All participants had different blood sugar levels including:

• healthy
• prediabetic
• diabetic

Dr. Christopher Rentsch, PhD, assistant professor of epidemiology at the London School of Hygiene & Tropical Medicine and lead author of this study explained to Medical News Today:

“We were interested to explore which risk factors drive known sex differences in the risk of heart disease between men and women with diabetes, and whether men or women with moderately elevated blood sugar below the threshold for diabetes are also at increased risk of heart disease.”

Upon analysis and after adjusting for age, the research team found both men and women with moderately elevated blood sugar levels below the threshold for diabetes were at increased risk for any type of cardiovascular disease.

“The finding that moderately elevated blood sugar below the diabetes threshold was associated with (an) increased risk of heart disease was not entirely surprising based on prior research in this area. For example, there is a recognized state of ‘prediabetes’ where blood sugar is elevated but not yet meeting the criteria for a diabetes diagnosis. Prediabetes is known to increase the risk of progressing to diabetes and potentially developing heart disease. Key novel contributions of our work were quantifying the risk of heart disease across a full range of blood sugar levels for both men and women and demonstrating these associations were largely explained by modifiable factors.”

— Dr. Christopher Rentsch, PhD, lead study author

Dr. Rentsch and his team also found a difference in risk levels between men and women.

Scientists found men with increased blood sugar levels below the threshold for diabetes had a 30% greater risk of developing cardiovascular disease. However, women with the same levels had a great risk of between 30–50%.

“Our study represents a meaningful step forward from decades of research on the link between diabetes and heart disease, which has long asserted that men and women with diabetes have differential risks of heart disease,” Dr. Rentsch said.

“Therefore, while robust quantification was still needed, the notion that moderately elevated blood sugar levels could be associated with greater risks of heart disease in women versus men was plausible based on existing scientific literature.”

“Our work strengthens the evidence by rigorously quantifying the higher relative risks in women across the full range of blood sugar levels,” he continued.

“Importantly, we discovered that differences between men and women in the risk of developing heart disease largely disappeared after we accounted for, in particular, measures of obesity and the use (of) preventative medications like antihypertensive and statin therapies.”

After reviewing this study, Dr. Nate Lebowitz, an attending cardiologist specializing in cholesterol and preventive cardiology care at Hackensack University Medical Center told MNT he was not surprised by its results.

Still, Dr. Lebowitz noted the findings convey an “important message” that the higher end of healthy — or otherwise minimally elevated — glucose levels were a marker for insulin resistance, which is why these people had a higher risk of heart disease.

“When it comes to diabetes and prediabetes, the risk of cardiovascular disease is not so much related to elevated glucose as it is to insulin resistance, which can be genetically determined, or related to excess body weight, a sedentary lifestyle, poor diet and often a combination of these factors. Insulin resistance is present in the earliest stages of prediabetes when glucose is still normal, or minimally elevated. (And) insulin resistance confers an elevated risk of cardiovascular disease (as) this study confirmed a higher risk in these patients.”

— Dr. Nate Lebowitz, cardiologist

And Dr. Yu-Ming Ni, a board-certified cardiologist and lipidologist at MemorialCare Heart and Vascular Institute at Orange Coast Medical Center in Fountain Valley, CA, agreed and provided more insight into how insulin resistance affects the cardiovascular system.

“Insulin resistance is where our body makes insulin but our tissues don’t really listen to it,” he explained. “As a result, blood sugar levels increase in the blood. It can cause the lining of the blood vessels to become damaged and so you can have more likelihood for plaque build-up on the lining of the walls of the blood vessels that can then lead to heart disease.”

“And we know that’s the case because patients with diabetes tend to have multiple blood vessel involvements,” Dr. Ni added. “When we do an angiogram, if you look at the arteries of the heart, we tend to see they have multiple blood vessels that are involved because of the long-standing exposure to damaging blood sugar.”

And the study researchers also reported a disparity between men and women when it came to receiving preventative medications.

Dr. Rentsch and his team found more men than women were on preventative antihypertensive and statin medications, suggesting a “prescribing gap” between men and women with similar blood sugar levels.

“Our findings support women being proactive in asking about medications like statins and antihypertensives as an option to help lower their risk if clinically appropriate,” Dr. Rentsch said.

“The decision to initiate preventive medications requires carefully weighing individual risks, benefits, and preferences. But this study provides backing for women to open a dialogue with their provider about whether preventive medications may be a suitable part of their overall cardiovascular risk reduction plan.”

Dr. Lebowitz commented this finding illustrates that, even to this day, women are not treated as well, as aggressively, or properly compared to men when it comes to identifying and preventing cardiovascular disease.

“The treatment of heart disease, hypertension, cholesterol, and diabetes is supposedly getting better for women, but there is still a disparity in care. This disparity is putting women at higher risk. This study proves that when these risk factors are addressed equally in both sexes — the risk factors related to glucose and insulin resistance — it makes a significant difference in outcomes. Doctors need to realize that women are at similar risk just as much as men.”

— Dr. Nate Lebowitz, cardiologist

Sometimes a person’s blood sugar, also known as blood glucose, can become too high. Certain factors may cause a person’s blood sugar to spike, even if they do not have diabetes. These may include:

There are a few different tests used to determine a person’s blood sugar levels.

One of those tests is the fasting blood sugar test, where a person’s levels are checked when they have not eaten. A fasting glucose reading of 99 mg/dL or below is considered healthy.

Another commonly used test is the A1C test, which measures a person’s average blood sugar levels over two to three months. An A1C test reading of 5.7% or below is considered healthy.

When a person’s blood sugar levels test in ranges above normal, it is considered high blood sugar, medically known as hyperglycemia. High blood sugar can signal either prediabetes or diabetes.

Symptoms of high blood sugar include:

If left untreated, high blood sugar levels can lead to a variety of health issues, including:

Previous research has also linked high blood sugar levels to an increased risk for certain heart conditions, including stroke and high blood pressure. Talk with your doctor if you’re concerned about your blood sugar levels and heart disease risk.