Research in recent years has shown certain types of arthritis are linked to a common form of heart disease. Learn more about this surprising link and what you can do to protect yourself.

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If you have arthritis, you know the importance of protecting your tender, painful joints. But did you know you should be taking the same care with your heart? For several years, doctors have recognized that people with rheumatoid arthritis (RA) and lupus face an increased risk of atherosclerosis, the common and potentially life-threatening problem that is known as "hardening of the arteries." Now they're beginning to understand why.

Investigators are starting to discover that arthritis and atherosclerosis may have a lot in common. Their findings do more than underscore the importance of heart-healthy habits in people with arthritis; they challenge the long-held beliefs about heart disease. Perhaps most importantly, these findings are opening the door to new heart disease treatments for everyone — whether they have arthritis or not.

Here's what we know now about atherosclerosis and how arthritis may play a role in the disease.

What Is Atherosclerosis?
Coming from the Greek words athero (meaning paste) and sclerosis (hardness), atherosclerosis is a general term used to refer to thickening and hardening of the arteries. While some thickening may occur naturally as we age (indeed, advanced age is a major risk factor), the main problem in atherosclerosis is the deposit of substances in the artery's inner lining. These substances include blood platelets, cholesterol, calcium and cellular waste products, which together form a sludge called plaque.

The problem with plaque occurs when it becomes so thick that it blocks blood flow through the artery or when the plaque ruptures and a blood clot forms on the artery's surface, much like a clot would form at the site of a cut on the surface of the skin. Whichever way blood flow is interrupted, the result can be a heart attack or stroke.

Although anyone can have atherosclerosis, certain factors, including lifestyle habits, can increase your risk. Such factors include family history, obesity, sedentary lifestyle, smoking, hypertension, high cholesterol levels, and having certain forms of arthritis.

How Does Arthritis Increase Risk?
No one knows exactly why atherosclerosis would be more common in people with RA or lupus, but those who study the problem and the literature on it offer some possible — and intriguing — explanations.

More or shared risk factors: The first, and simplest, explanation for why some people with arthritis are prone to develop atherosclerosis is that they are likely to have lifestyle risk factors, says Susan Manzi, MD, assistant professor of medicine and epidemiology at the University of Pittsburgh and a leading expert on arthritis and heart disease risk. For example, many people with lupus or RA may be overweight or have a sedentary lifestyle because of joint pain and difficulty exercising.

Other risk factors for artherosclerosis may be problems associated with some forms of arthritis. Hypertension, for example, is a common condition in lupus, says Dr. Manzi.

Damaging medications: Another explanation for why atherosclerosis can go hand in hand with arthritis is the medications taken for arthritis-related conditions can either directly or indirectly lead to atherosclerosis. The most commonly implicated drugs are glucocorticoids (chiefly prednisone), which are prescribed for many inflammatory forms of arthritis. Prednisone may indirectly lead to atherosclerosis by predisposing you to other risk factors. For instance, prednisone therapy can increase blood lipids (fats), leading to high cholesterol; it can induce hypertension; cause weight gain and, at high doses, even cause diabetes. All of these are risk factors for atherosclerosis.

All of that aside, there are more direct ways glucocorticoids can lead to atherosclerosis. For example, some scientists think that atherosclerosis begins with damage to the artery's innermost layer, the endothelium. Glucocorticoids may damage endothelium by interfering with the chemical prostacyclin (which inhibits blood clotting) in endothelial cells. Glucocorticoids may also interfere directly with the function of blood platelets, making them more likely to form clots.

Methotrexate, another commonly prescribed arthritis medication, has been shown to increase levels of homocysteine, an amino acid in the blood. High levels of homocysteine have been linked to an increase of cardiovascular disease.

The disease process. Probably the most intriguing explanation of the atherosclerosis-arthritis connection involves a rethinking of heart disease itself. While doctors know that plaque-narrowed arteries are more likely to be blocked by clots, it turns out thick deposits of this arterial sludge aren't always the culprits. The biggest enemy to arteries may, in fact, be the body's own immune system. Sound familiar?

Some researchers believe the inflammatory response associated with autoimmune diseases or other causes of endothelial damage may make plaque likely to rupture and cause fatal clots. In fact, according to Peter Libby, MD, chief of cardiovascular medicine at Harvard Medical School, inflammation in the artery walls may be as big of a risk factor for heart attacks as high cholesterol, and periodic tests for inflammation, in combination with cholesterol screenings, could better predict who's at risk for a heart attack.

The Intriguing Link
Doctors studying the inflammation angle on heart disease think atherosclerosis in anyone may begin as early as adolescence with some type of damage or irritation to the arteries. Sources of this damage may include infections and possibly immune complexes that are formed in some autoimmune diseases. These complexes can deposit on blood vessel walls causing damage that triggers inflammation.

Once the vessel is damaged initially, immune cells are dispatched to take care of the problem, but sometimes — as is the case with diseases like RA and lupus — the immune system doesn't know when to quit. The result, in this case, is chronic inflammation that may allow plaque to take a foothold.

The endothelium, which is damaged in atherosclerosis, plays an important role in any inflammatory form of arthritis. Immune cells traveling down the bloodstream must pass through the endothelium to reach the target, whether it be a joint or a kidney. Dotting the endothelium are so-called adhesion molecules that allow these immune cells to adhere to and pass through the vessel wall. These same adhesion molecules may play an important role in atherosclerosis because they promote the migration of inflammatory cells that lead to plaque formation in the vessel walls, says Dr. Manzi.

Keys to Treatment
Recognizing the similarity and connection between atherosclerosis and inflammatory diseases such as lupus and RA has the potential to pay off in the understanding and treatment of both types of diseases. For example, "The biologic therapies that are down-regulating the inflammatory immune function in [RA] patients may help prevent atherosclerosis in patients without arthritis," Dr. Manzi says.

Already, etanercept (Enbrel), the first biologic agent to be approved for treating RA, is being tested in people with congestive heart failure — a condition in which the heart is unable to pump strongly enough to maintain normal circulation, often because of damage caused by atherosclerosis or hypertension. Anti-inflammatory medications, primarily aspirin, prescribed for arthritis are also used to treat and prevent cardiovascular disease, as well as strokes.

"The problem with [stronger] inflammatory drugs like prednisone, is they come with baggage, such as weight gain and hypertension," says Dr. Manzi. "If we could [control] inflammation without these adverse effects, we might have a drug that works for lupus and heart disease. Right now, biologics look promising, but we need more research to determine what works best."

What You Can Do Today
Until such research pays off, your best bet for avoiding atherosclerosis is to minimize your known risk factors, experts say. While you can't change the fact that you have RA or lupus, other risk factors are fixable. Fixing those risk factors means keeping your blood pressure and cholesterol level low (it's important to have both checked regularly), exercising, not smoking, avoiding harmful drugs when possible and consuming a diet rich in folic acid (and/or taking a folic acid supplement) to help lower homocysteine levels associated both with arthritis and methotrexate treatment.

Perhaps most important is awareness, Dr. Manzi says. "Rheumatoid arthritis and lupus are diseases more commonly occurring in women, who tend to think they are protected from heart disease until they are past menopause. For most women that holds true, but not for women with these diseases. They must recognize that they are at high risk for heart disease, even at a young age, and correct modifiable risk factors."

When it comes to taking measures to prevent a potentially deadly problem like atherosclerosis, it's never too soon to start. For people with arthritis, this is especially true, says Dr. Manzi.

Mary Anne Dunkin is a contributing editor to Arthritis Today.