A woman uses a watch and meter to check her blood sugar levelsShare on Pinterest
People with elevated blood sugars can be at risk for heart disease even if they don’t have diabetes. Andriy Onufriyenko/Getty Images
  • People with blood sugar levels high enough to be diagnosed with prediabetes, but not diabetes, have an increased risk of heart failure and stroke.
  • Women with prediabetes had higher cardiovascular risks than men, but this was reduced when lifestyle factors and medications were considered.
  • Having lower normal blood sugar levels reduced heart-related risks even more.

People with elevated blood sugar levels have a 30% to 47% higher risk of developing a cardiovascular disease problem such as stroke or heart failure, even when they have prediabetes, a new study shows.

Prediabetes is a health condition where blood sugar levels are higher than normal, but not high enough to be diagnosed as type 2 diabetes.

Researchers also found that women have a higher risk of developing a cardiovascular problem than men do — compared to people with normal blood sugar levels.

However, the differences in relative risk between men and women largely went away after researchers took into account lifestyle factors and medication use.

Dr. Daniel Kiss, an interventional cardiologist at Jersey Shore University Medical Center in New Jersey and Hackensack Meridian Health AngioScreen medical director, said this study shows that when it comes to blood glucose levels, there is a spectrum of cardiovascular risk.

“Essentially, it’s not just whether or not someone has diabetes, but all spectrums of glycemic control play a role,” he told Healthline. In addition, “it’s important to note that this risk can be lessened by use of medication [indicated] in the study.”

People with diabetes, especially if it is uncontrolled, are at high risk for cardiovascular disease, said Dr. Sharleen Sidhu, an endocrinologist at MarinHealth Endocrine & Diabetes Care, UCSF Health Clinic in California.

This includes damage to small blood vessels, which can impact the kidneys, eyes, and nerves. It can also cause damage to larger blood vessels, which can lead to stroke and congestive heart failure.

Because “prediabetes is a precursor for developing type 2 diabetes,[people with prediabetes] should also be concerned and aware of microvascular and macrovascular complications,” Sidhu told Healthline.

The study, published August 9 in The Lancet Regional Health, included more than 427,000 people — roughly half men and women — taking part in the UK Biobank, a long-term observational study.

Participants, age 40 to 69 years at enrollment, were recruited in the United Kingdom between 2006 and 2010 and followed through to 2021.

Researchers assigned participants to a category based on their average blood sugar level over the past 3 months (HbA1c level) at the first study visit: low-normal, normal, prediabetes, or diabetes (either diagnosed or undiagnosed).

Using biobank data, researchers identified participants who had one or more of the following cardiovascular disease problems during the study period: coronary artery disease, atrial fibrillation (AFib), deep vein thrombosis, pulmonary embolism, stroke, and heart failure.

After adjusting for age, researchers found that men with prediabetes or undiagnosed diabetes had around a 30% increased risk of developing a cardiovascular disease problem compared to men with “normal” blood sugar levels.

In contrast, women with prediabetes or undiagnosed diabetes had a 47% and 33% increased risk, respectively, compared to women with “normal” blood sugar levels.

In men with diagnosed diabetes, the risk of a cardiovascular disease problem was 55% higher. Women with diagnosed diabetes had double the risk.

The differences between men and women largely went away when researchers took into account obesity — which can be reduced with lifestyle changes — and the use of medications to lower blood pressure or cholesterol (statins).

However, men with prediabetes or undiagnosed diabetes still had a higher risk of coronary artery disease, even after this adjustment.

Researchers also found that men and women with low-normal blood sugar levels had a lower risk of developing a cardiovascular disease problem.

“The study shows what we already know,” said Sidhu, “that when you have better controlled blood sugars or normal blood sugars, there is a reduction in complications such as cardiovascular disease, stroke, heart attack, elevated blood pressure and high cholesterol.”

The results don’t apply to people with type 1 diabetes, because people with this condition were not included in the analysis.

In addition, participants in the study tended to have more healthy lifestyle behaviors and lower rates of cardiovascular disease than the general population, researchers said, so the findings may be different for less healthy groups.

And because of the narrow age range of participants, the results may not apply to younger or older people.

Overall, the findings fit with a recent systematic review and meta-analysis which found that people with prediabetes had a higher risk for cardiovascular disease problems.

Another meta-analysis showed that people without diabetes who took blood-pressure-lowering medications saw similar drops in cardiovascular disease risk, compared to those with diabetes.

This supports the wider use of medication treatments for the prevention of cardiovascular disease in people without diabetes, the researchers write.

“Our results suggest that the increased risks seen in both men and women could be mitigated through modifiable factors, including weight reduction strategies and greater use of antihypertensive and statin medications,” study author Krishnan Bhaskaran, PhD, a statistical epidemiologist at LSHTM, said in a release.

However, the new study found that men were more likely than women to be using these medications, which suggests that women are not prescribed these preventative drugs at the same rate as men with similar blood sugar levels.

“Despite all of our efforts, studies still seem to suggest that women at risk are undertreated compared to their male counterparts,” said Kiss, although he cautions that the study doesn’t have any data on why this difference between men and women exists.

Dr. Alexandra L. Kharazi, a cardiothoracic surgeon with CVTS Medical Group in Chula Vista, Calif., said diabetes is of particular concern for women.

Women “who are diabetic are much less likely to have symptoms, and their cardiovascular disease may go much longer being undiagnosed,” she told Healthline. “This is the patient population that should be proactive in seeing a doctor and even asking about being screened for cardiovascular disease.”

Sidhu pointed out that people with prediabetes typically have several years before they develop diabetes.

“So primary prevention strategies to keep blood sugar in the normal range early on will reduce the risk of diabetes, thus reducing the risk of cardiovascular complications down the line,” she said.

Although people with prediabetes have an increased chance of developing type 2 diabetes, as well as heart attack and stroke, lifestyle changes can prevent or delay type 2 diabetes and other health problems.

“Prediabetes is a warning signal, not a final diagnosis. It is an opportunity to implement lifestyle changes and potentially prevent the onset of type 2 diabetes and associated cardiovascular risks,” Kelsey Costa, MS, RDN, a registered dietitian representing the National Coalition on Healthcare, told Healthline.

People with prediabetes should eat a balanced diet that is low in refined carbohydrates, saturated fat and added sugars, she said. In addition, they should focus on eating complex carbohydrates (such as whole grains), non-starchy vegetables and raw fruit.

Costa recommends the Dietary Approaches to Stop Hypertension (DASH) diet and the green Mediterranean diet (which avoid red meat and processed meats altogether), which have been show to have positive health benefits.

In addition, “research has demonstrated the importance of exercise for prediabetic and obese individuals” for improving insulin sensitivity, she said, adding that this should include both cardiovascular and strength training components.

While lifestyle changes such as healthy eating and regular exercise can reduce the risk of developing type 2 diabetes, other factors are involved in determining a person’s risk, including genetics.

As a result, “it is important to have regular health check-ups and surveillance for potential risk factors,” said Costa, “including blood sugar testing, cholesterol/lipid checks, blood pressure monitoring and other preventative screening.”

A new study from UK researchers found that people with blood sugar levels high enough to be diagnosed with prediabetes, but not diabetes, have an increased risk of heart failure and stroke.

Lifestyle changes like exercise and healthy diet can reduce this risk, say experts.