When determining someone's risk of developing heart disease, there are a number of factors to consider. High blood pressure, high cholesterol, obesity and smoking are probably some of the first that come to mind. Other risk factors that can't be controlled can also have an impact, including family history, age, gender and ethnicity.
But what underlies the connection between these risk factors is a common thread: inflammation.
"Inflammation is essentially your body's ability to repair stress," says Ashley Simmons, MD, a cardiologist at The University of Kansas Health System. "You want your body to have that ability. But it's the chronic, low-level inflammation that can really cause a lot of problems."
When your body is injured – say, you sprain your ankle – a cascade of defense mechanisms is quickly set in motion to repair the damage and bring relief. Bruising, swelling and tenderness are all signs that inflammation is doing its job: bringing blood to the area, keeping the ankle tight (to prevent further injury) and limiting your range of motion to avoid more aggravation.
This is acute inflammation.
But when your body lives in a constant state of stress – say you have a chronic condition like lupus or uncontrolled high blood sugar – that alarm response is always on. The irritation never has time to heal and this results in a cycle of re-injury that causes serious stress to your body, especially the heart. This is how chronic inflammation occurs.
How inflammation affects your heart
While most people think of high-cholesterol, fatty foods as the primary culprit for unwanted plaque in the arteries, new research has shown that cholesterol in the diet doesn't necessarily equate to cholesterol in the blood. And cholesterol isn't the only influential factor. Inflammation has been shown to impact the endothelium, or lining of the arteries responsible for good heart health.
"When you have elevated levels of C-reactive protein, which is a marker of inflammation, the endothelium does not function normally," says Dr. Simmons. "This disruption can result in the progression of plaque development or a plaque rupture, which is a heart attack."
Exactly how inflammation affects the lining of the arteries is a complex process, and one that is still being researched. Dr. Simmons explains that the endothelium plays a protective role in the blood vessels and certain factors are responsible for making sure it functions properly. One of these factors is nitric oxide, which is produced by a special enzyme called nitric oxide synthase. Inflammation inhibits the production of this enzyme, which then lowers levels of nitric oxide, causing the endothelium to function improperly. This affects the health of the arteries and can lead to plaque development and, ultimately, cardiovascular disease.
How inflammation occurs
According to Dr. Simmons, most chronic inflammation occurs from a pre-existing condition or chronic autoimmune disease, such as rheumatoid arthritis. But inflammation can also occur as a result of prolonged stress or even a highly processed diet.
"When you're taking in refined foods, the liver works overtime to process all the sugar and our blood sugar levels go up," says Nicolette Jones, a cardiovascular clinical dietitian at The University of Kansas Health System. "It's a pretty stressful process for the body. And there's research that shows that those intense blood sugar spikes damage our circulatory system and our blood vessels."
Twenty years ago, during what Jones refers to as the "SnackWell's® Age," low-fat, low-calorie, highly processed foods were considered "safer" for heart health than, say, full-fat butter. But opinions in the nutrition and cardiology communities have changed.
"We are finding more and more that certain fats are helpful in reducing inflammation, and that refined sugars, empty calories, and refined grains are what impact diabetes and the accumulation of elevated cholesterol," Jones says. "Trans fats we now know can increase inflammation as well, and embed themselves in cells and cause plaque build-up."
Inflammation can occur in other ways, too, including excessive exercise. While most people think of exercise as a good thing (and it is – moderate exercise can lower both stress and inflammation), overtraining can cause inflammation of the joints. When this inflammation persists for long periods of time, and the body isn't able to heal the injury, chronic inflammation results. This is why we hear stories about ultra-fit marathon runners who suffer sudden cardiac arrest.
"Excessive endurance exercise can increase inflammation, and that results in structural changes in the arteries and heart rhythm abnormalities, too," says Dr. Simmons. "When we look at long-distance extreme athletes, they have a much higher risk of atrial fibrillation. That's probably partly due to the levels of inflammation and the hemodynamic stress they put on their heart."
How much is too much?
Knowing that chronic inflammation has a negative impact on your heart is a first step toward better cardiovascular health, but where do you draw the line? How long can you stay at a stressful job before your heart suffers the consequences? How many sugar-loaded sodas before it's too much?
"I really don't know that there's a defined time period or amount to be considered chronic," says Dr. Simmons. "I think the key is, in patients with chronic autoimmune disease or who suspect chronic inflammation, seeking a cardiac risk assessment can be beneficial."
There are several different cardiac risk scores that can help predict your risk of developing heart disease, but one in particular identifies your levels of inflammation by measuring C-reactive protein – a marker of inflammation in the body. The test, called the Reynolds risk score, also accounts for factors such as age, blood pressure, cholesterol, family history and history of smoking.
"The higher the number of C-reactive protein, the more likely your doctor may be concerned that there is some risk for future heart issues," explains Jones.
Those who are worried about their heart health, or whose risk scores are elevated, can consider a coronary calcium scan. The test, Simmons says, is like a chest X-ray that takes a picture of the heart and assigns a score to the amount of calcified plaque visible in the arteries. The tests are self-referred and can cost on average between $50-$100 out-of-pocket.
Taking charge of your future
The role of inflammation in heart disease remains an evolving area of study. As researchers continue to examine exactly how inflammation affects not only the heart, but also the risk factors that impact heart health, we may soon find that inflammation is involved in heart disease at nearly every level.
But for those with chronic conditions, all hope isn't lost. According to Dr. Simmons, even people who have suffered prolonged inflammation can change the course of their heart health.
"I think there's always an opportunity for repair," Dr. Simmons says. "It comes down to decreasing stress, making sure your blood sugar is stable, getting cholesterol under control, eating right and exercising in moderation."
It comes down to decreasing stress, making sure your blood sugar is stable, getting cholesterol under control, eating right and exercising in moderation. – Ashley Simmons, MDCardiologist