Shining a light on the diabetes–heart disease connection

If you have diabetes, you're twice as likely to have a heart attack or stroke than someone without diabetes — even if you keep your blood sugar under control most of the time. In fact, recent research suggests this elevated cardiovascular risk is present as early as 30 years prior to a diagnosis of type 2 diabetes (see "Higher heart risks before diabetes detection"). Typically diagnosed after age 45, type 2 diabetes accounts for more than 90% of diabetes cases in the United States.

The new findings support the long-held observation of the shared underlying causes of diabetes and heart disease, says Dr. Deborah Wexler, chief of the Diabetes Unit at Harvard-affiliated Massachusetts General Hospital. "It's known as the common soil hypothesis, which dates back to the mid-1990s," she says. The "soil" refers to risk factors that contribute to both conditions—especially the tendency to accumulate fat in the middle of the body. Also known as visceral or abdominal obesity, this problem typically occurs in tandem with high blood pressure, unhealthy lipid levels, and elevated blood sugar. This cluster of signs and symptoms is also known as metabolic syndrome, says Dr. Wexler.

A diabetes primer

In type 2 diabetes, the body is often resistant to insulin, the hormone made by the pancreas that enables cells throughout the body to absorb glucose (sugar) for energy. As a result, muscle, fat, and liver cells can't easily absorb glucose from the blood, causing blood sugar levels to rise. In response, the pancreas tries to keep up with the demand by churning out more insulin. But over time, the insulin-producing cells in the pancreas falter, leading to prediabetes and eventually diabetes.

Belly fat, which makes hormones and other substances that trigger chronic inflammation, is a common hallmark of insulin resistance. Another is physical inactivity. Exercise makes your body more sensitive to insulin and builds muscle, which absorbs blood glucose.

While a poor diet and being sedentary clearly contribute to diabetes, genetic factors play a role as well. Having one parent with diabetes translates to a 40% lifetime risk of the disease; if both parents are affected, that risk rises to 70%, according to some estimates. Still, people with a high genetic risk can prevent diabetes with healthy habits, says Dr. Wexler. "In a study that included identical twins at risk, the twin who maintained a healthy weight did not get diabetes, but the one who gained weight did," she says.

More diabetes prevention tips

The 2025 Standards of Care in Diabetes from the American Diabetes Association includes several updates targeted to lifestyle changes for people with diabetes, such as a recommendation to do strength training (such as lifting weights or using resistance bands) two to three times per week. The benefits include preventing muscle loss and improving insulin sensitivity and overall metabolism.

One diet-related tip encourages drinking water instead of beverages sweetened with sugar or artificial sweeteners. Another is a recommendation to eat more plant-based protein and fiber—a common refrain for heart-healthy eating (see "The portfolio diet: A smart investment for your heart" in the February 2024 Heart Letter).

Beyond blood sugar control

People with diabetes tend to focus on keeping their blood sugar values within range. That's important because uncontrolled high blood sugar can damage tiny blood vessels throughout the body, causing vision problems, nerve damage, and kidney disease. "But most people don't realize that the leading cause of death in diabetes is cardiovascular disease," says Dr. Wexler. Doctors have long encouraged aggressive treatment of heart-related risk factors for people with diabetes — namely, keeping blood pressure and cholesterol levels in a healthy range and quitting smoking. Over the past decade, though, two new classes of drugs, SGLT-2 inhibitors and GLP-1 receptor agonists, have emerged that not only lower blood sugar but also reduce heart-related risks (see "Diabetes drugs with proven heart benefits").

Major medical societies, including the American College of Cardiology, recommend these drugs in people with type 2 diabetes who either have or are at high risk of heart disease, regardless of their A1c level, says Dr. Wexler. (The A1c test, commonly used for monitoring diabetes, provides a three-month average measure of blood sugar. Levels of 6.5% or higher are classified as diabetes.)

Both classes of medications are underused, although the use of the GLP-1 drugs (especially semaglutide) in people with diabetes has risen in recent years. Taken weekly by self-injection, semaglutide and tirzepatide can lead to dramatic weight loss, although they may cause nausea and can be expensive, even with insurance coverage. (Both drugs are prescribed in different formulations for weight loss: semaglutide under the name Wegovy, and tirzepatide under the name Zepbound.) Cardiologists and nephrologists (who treat kidney disease) may be more comfortable prescribing SGLT-2 inhibitors, which are taken in pill form and have been around for more than a decade now, Dr. Wexler notes. Both semaglutide and SGLT-2 inhibitors have kidney benefits for people with chronic kidney disease.

The bottom line

If you have diabetes, ask your physician whether you should add one of these drugs to your current medication regimen. If you don't, follow your physician's advice regarding when and how often you should be screened for diabetes. For people who are overweight, the latest guidelines suggest screening every three years starting at age 35.

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