Heart Health and Diabetes
Take a deep dive into the who, what, and why of the heart
For most of us, the heart is our childhood introduction to anatomy. Understanding its importance, we cross our hearts to pledge promises and make cute (though anatomically incorrect) drawings as gifts on Valentine’s Day.
But this early knowledge of the heart doesn’t always carry over into adulthood. Cardiovascular disease remains the No. 1 cause of death in the United States, according to the Centers for Disease Control and Prevention (CDC), accounting for nearly 1 in 4 deaths annually. For people with diabetes, the chance of dying from heart disease doubles.
Knowing how the heart works is an important part of reducing heart disease deaths. February is American Heart Month, so we’re breaking down everything you need to know about this vital organ.
The Heart of the Matter
At its most basic, the heart supplies blood throughout the body. Our brain, kidneys, muscles—everything requires a steady supply of oxygenated blood in order to function. But accomplishing that simple goal is more complicated than you might think. “The way I like to distill it down for patients is that the heart has three systems,” says Luke Laffin, MD, a preventive cardiologist at the Cleveland Clinic. “Pump, rhythm, and plumbing.” Diabetes can affect all of these.
Most of us are familiar with the pumping function, the mechanism by which the heart’s four chambers move blood. This is what you feel when you put your hand to your chest. Blood from the body flows into the right atrium and is then pumped into the right ventricle. That pumps blood to the lungs, where it picks up oxygen. Once blood has gone through the lungs, it returns to the heart, moving through the left atrium and left ventricle before being pumped out to the rest of the body.
Rhythm refers to your heart’s electrical system. This tells your heart how many times to pump per minute (ideally 60 to 100 when at rest). Electrical signals also ensure the four chambers of your heart are working in conjunction.
Then there’s the plumbing, the arteries and veins that the blood moves through to reach your organs and muscles. These systems work in concert, sending blood to the lungs to collect oxygen, delivering that enriched blood to the body, and returning the deoxygenated blood back to the lungs to prepare for its next delivery.
When we talk about heart health, all of these systems are part of the conversation.
Is Your Heart at Risk?
If something goes wrong with any one of these complex systems, it’s called cardiovascular disease (CVD), though it’s commonly referred to simply as heart disease. Beneath the umbrella of CVD, there are several conditions, including coronary artery disease, heart attack, stroke, and peripheral artery disease. (See “Types of Cardiovascular Disease.”)
No matter the type of CVD, all share similar risk factors. Two of the biggest, when combined, can cause major problems. “High blood pressure and high cholesterol conspire to increase the risk of coronary artery disease,” says Micah Eimer, MD, a cardiologist at Northwestern Memorial Hospital in Chicago, part of Northwestern University’s Feinberg School of Medicine.
Cholesterol is a blood fat, or lipid, that’s important for creating healthy cells, but if your body has too much, it begins to accumulate on the walls of your arteries. This narrows and obstructs your arteries, making it more difficult for blood to pass through.
But not all cholesterol is created equal. “LDL, or low-density [lipoprotein], can easily accumulate and is the main source of these blocks,” says Om Ganda, MD, medical director of the lipid clinic at the Joslin Diabetes Center in Boston. “So we always talk about keeping LDL cholesterol as low as you can.”
On the other hand, high-density lipoprotein (HDL cholesterol) is good for you. It clears your arteries by removing excess cholesterol, preventing blockages, and helping your blood flow smoothly. “The higher the HDL, the lower the risk of heart disease,” Ganda says.
He also points to triglycerides, another type of lipid that should be kept low to reduce your risk of blockage.
For people with diabetes, especially those with type 2, insulin resistance can lead to high LDL cholesterol and triglycerides, and low HDL cholesterol. According to the 2020 Standards of Medical Care in Diabetes from the American Diabetes Association (ADA), keeping blood glucose levels in a healthy range can help improve your overall cholesterol, especially if you have high triglycerides.
High blood pressure, or hypertension, is another major risk factor for the development of CVD. “High blood pressure exerts a negative effect on the heart by increasing the work that the heart has to do to circulate the blood,” Eimer says. “This can result in thickening of the heart muscle, enlargement of the heart, and eventually an inability of the heart to pump blood effectively.”
These conditions can lead to coronary artery disease or heart failure over time, but high blood pressure, high LDL cholesterol, and high triglycerides combined can also present more immediate dangers. “A blockage formed by high cholesterol is usually unstable,” Ganda says. “If [blood] pressure is high, the block is more likely to rupture and cause blood clots, leading to heart attack or stroke.”
The Diabetes Factor
There’s a connection between CVD and diabetes—and it’s significant. “Patients with diabetes are essentially treated as if they already have heart disease,” says Michelle Kittleson, MD, a cardiologist in the Smidt Heart Institute at Cedars-Sinai hospital in Los Angeles. According to the CDC, an adult with diabetes is hospitalized with cardiovascular disease every 80 seconds in the United States. And an American adult with diabetes is hospitalized for stroke every 2 minutes. “The risk is so high, we treat them aggressively for prevention measures,” she says.
Even when their blood glucose is within goal range, people with type 1 and type 2 diabetes have a greater chance of developing CVD. Their increased likelihood of heart disease risk factors, such as high blood pressure and high cholesterol, plays a role, as does chronic inflammation, which can be an initial cause of artery damage. All of this is compounded if a person is overweight.
People with type 1 may have symptoms of heart problems at an earlier age because they’ve likely lived with diabetes longer. “If you see a person with type 1 diabetes who complains of chest discomfort, then you have a high index of suspicion that they may have coronary artery disease,” Kittleson says.
Elevated blood glucose, which can damage the blood vessels over time, also adds to the risk. Keeping blood glucose in goal range can help protect the heart. “The better the diabetes is controlled, the happier we [cardiologists] are that the patient is doing everything possible to minimize it as a risk factor,” Kittleson says.
Still, the greatest risk factor is one that eventually affects all of us: aging. “When you age,” says Ganda, “your heart muscles can become weak, and your blood vessels can develop deposits from cholesterol.”
The Gender Divide
Men and women experience cardiovascular disease slightly differently. Scientists aren’t entirely sure why, but estrogen helps protect the heart in premenopausal women by causing more favorable cholesterol profiles, lowering blood pressure, and reducing inflammation. But this isn’t necessarily the case for women with diabetes. “Diabetes affects both genders equally,” Ganda says. “Normally, estrogen protects women. But if you have diabetes, the estrogen protection is lost, starting even before menopause.”
Gender bias also plays a role. CVD is the leading cause of death for both women and men, but assumptions about men being at greater risk mean that women are often under- or misdiagnosed.
“Women sometimes tend to have less-classic symptoms,” Kittleson says. “The crushing chest pain that we all think about as a classic sign of heart disease, women may get less. They may have more nonspecific symptoms, like fatigue or nausea.”
Women should tell their doctors if they’re experiencing nontraditional symptoms of heart disease, especially if they have other risk factors.
A Heart-Healthy Life
A diabetes-friendly lifestyle goes hand in hand with heart health. “Lifestyle changes, such as losing weight, eating healthy, and getting regular exercise, combined with medications to treat blood glucose levels, reduce the risk of heart problems,” says Andrew Calvin, MD, a cardiologist with the Mayo Clinic Health System.
Exercise is one of the best ways to prevent heart disease. It improves blood pressure, lowers LDL cholesterol, raises HDL cholesterol, and helps manage diabetes and related complications. Regular exercise will also help your cardiologist get a better sense of your heart health.
“If I know that you’re exercising at a reasonable level and not having any symptoms, then everything is going well. It’s a daily stress test,” Eimer says. “On the other hand, if you’re exercising and you’re having symptoms, that’s an early warning sign that we may need to look into something.”
The Standards of Medical Care in Diabetes recommends at least 150 minutes of moderate- to vigorous-intensity aerobic exercise each week, two to three strength-training sessions per week, and two to three sessions a week dedicated to flexibility and balance exercises.
When it comes to food, fresh is best. Kittleson tells her patients to avoid packaged foods. “Focus on whole foods, whether that’s meats, grains, fruits, or vegetables, and you’re already winning the game,” she says.
Studies have linked a Mediterranean-style eating plan—which limits red meat and emphasizes fruits, vegetables, whole grains, legumes, healthy fats, and fish—to better blood glucose management and a reduced risk of CVD. The fiber in foods such as fruits, veggies, legumes, and nuts can help improve cholesterol levels. And the omega-3 fatty acids in fish such as trout and salmon reduce the type of inflammation that can lead to heart problems, help lower cholesterol and triglyceride levels, and have been linked to a lower risk for heart disease. A reduced-salt diet can help prevent or treat high blood pressure.
Cholesterol-lowering statin medications may make a difference—even if you don’t have heart disease. The Standards of Medical Care in Diabetes recommends that people with diabetes who don’t have CVD take a moderate-intensity statin medication beginning at age 40.
If you’re a smoker, quit. Not only does smoking shorten your life and worsen blood glucose management, but it also raises your risk of CVD. Nearly a third of all deaths from coronary artery disease are due to smoking and secondhand smoke, according to the American Heart Association. “Smoking increases the risk of everything bad and causes nothing good,” Kittleson says.
Of course, lifestyle changes alone aren’t always enough. Medication may be necessary to help lower cholesterol and manage blood pressure.
Treating the Heart
Maintaining healthy blood glucose, blood pressure, and cholesterol levels is key for preventing heart problems, and it’s an important aspect of managing diagnosed cardiovascular disease, too. If you’ve been diagnosed with heart disease, your doctor may prescribe a medication to treat your specific condition. There are a range of medications for treating heart failure, for instance, including ACE inhibitors and beta blockers. Aspirin is a common treatment for people who have had a heart attack or stroke. And the Standards of Medical Care in Diabetes recommends statin therapy for people with diabetes who have CVD or who have a high risk of CVD.
Your doctor may also adjust your diabetes medication. Research has found that glucose-lowering drugs in the SGLT-2 inhibitor or GLP-1 receptor agonist classes may also protect the heart in people with type 2 diabetes and diagnosed CVD. “Both of these classes are increasingly being used by primary care physicians and endocrinologists in patients with diabetes to protect the heart, on top of medicine like metformin,” Laffin says.
Some cases may also call for surgical intervention. A study published in 2018 in the European Heart Journal found that type 2 diabetes increases the need for a pacemaker, a device that helps regulate erratic heartbeats.
For those with artery disease, stent procedures can be performed to open blocked arteries, while bypass surgeries reroute blood flow around a blocked artery. Even after surgery, steps should be taken to lower blood pressure, LDL cholesterol, and triglycerides.
Get Screened Early
Many people don’t start thinking about heart health until middle age, but it’s never too early to start, especially if you have diabetes. “People should know their numbers,” Laffin says. “Know your body mass index [BMI, a ratio of weight to height used to estimate how close a person is to a healthy weight], blood sugar, and blood pressure. Those are all important and generally done by primary care doctors.” If these numbers put you at a higher risk, your primary care doctor can perform a more detailed assessment and, if necessary, refer you to a cardiologist.
“I see patients between their 20s and 60s,” Eimer says. “The earlier the better, because if there is a problem, it gives us an opportunity to change the course of the disease.” This is especially true for people with type 1 diabetes, who have generally lived with diabetes longer and had more time for high blood glucose to affect the heart.
If you have diabetes, you’ll want to have your blood pressure measured at every health care appointment; blood pressure targets are individualized, but in general the ADA recommends a target of less than 140/90 mmHg.
The ADA recommends a cholesterol test at the time of a diabetes diagnosis and at least every five years thereafter (your doctor may request more frequent checks based on how long you’ve had diabetes). Aim for an LDL level of less than 100 mg/dl, though your doctor may recommend a target of less than 70 mg/dl if you already have CVD or have a high risk.
Know Diabetes by Heart
Learn more about the connection between diabetes and heart health at knowdiabetesbyheart.org. This joint initiative of the American Heart Association and the American Diabetes Association aims to reduce cardiovascular death, heart attack, stroke, and heart failure in people with type 2 diabetes. Find resources for living a healthful life, learn how to prevent heart problems, test your diabetes know-how, and sign up to get more information.