FRIDAY, May 6 (HealthDay News) -- People with two common inflammatory diseases stand a higher chance of developing a heart condition that is strongly associated with stroke, a new study suggests.

The study, done at the University of Arkansas for Medical Sciences, found that patients with lupus and rheumatoid arthritis have a 60 percent increased risk for atrial fibrillation, an abnormal heart rhythm (arrhythmia) linked to stroke.

Pointing to a recent jump in atrial fibrillation cases, one of the study's authors said it was important to understand all the possible sources of the disease.

"We are in the middle of an epidemic of AF (atrial fibrillation)," said Dr. Abhishek Deshmukh, a cardiology fellow at the University of Arkansas for Medical Sciences Medical Center in Little Rock and one of the study's authors. "The numbers have gone sky high as people are living longer. AF tends to affect older people more."

About 2.2 million Americans have atrial fibrillation, according to the American Heart Association. The condition causes the heart to beat erratically and fail to pump all the blood out of the atria, two upper heart chambers. Because the blood pools, it may produce clots, which the heart "throws" from the chamber; the clots may then lodge in an artery in the brain, causing a stroke. About 15 percent of strokes occur this way, according to the association.

Deshmukh said researchers suspected that atrial fibrillation might be linked to systemic lupus erythematosus (SLE) and rheumatoid arthritis because the two autoimmune conditions cause inflammation, which scientists believe plays a role in heart disease. Almost 3 million Americans have one of the two diseases, according to the Arthritis Foundation and the Lupus Foundation of America.

Atrial fibrillation undermines people's quality of life and increases the risk of dying, said Deshmukh, adding that it is associated with congestive heart failure, diabetes, and high blood pressure.

Signs of atrial fibrillation include fluttering of the heart, dizziness, sweating, fatigue, confusion, weakness, shortness of breath and anxiety, although some patients display no symptoms. Many drugs are used to treat it, including the anticoagulant warfarin, which can reduce the risk of death by 68 percent for those with the illness, according to the heart association.

The study findings were slated to be presented Friday in San Francisco at the Heart Rhythm Society meeting.

The study, taking information from a large national database, looked at 416,786 patients older than 65, who were discharged from 1,200 hospitals around the United States after treatment for atrial fibrillation. The study controlled for factors such as age, sex, demographic information, and other illnesses.

In an initial analysis, 2.73 percent of patients with rheumatoid arthritis or lupus were found to have atrial fibrillation, compared to 1.7 percent for those unaffected by either condition.

After adjusting for confounding factors, the researchers found frequency of the heart arrhythmia was 1.6 times higher in patients diagnosed with one of the autoimmune conditions, an increased risk of 60 percent.

While the study found an association between the two diseases and the heart condition, it did not prove a cause-and-effect. And because it was presented at a medical meeting, its findings should be considered preliminary until published in a peer-reviewed journal.

Both lupus and rheumatoid arthritis are genetically based but are believed to have environmental triggers, according to Dr. Olivia Ghaw, a rheumatologist at Mount Sinai Medical Center in New York City. Women are far more likely to be affected, with estrogen playing a possible role, but no definitive answers have been found, she said.

Ghaw said that because the two autoimmune diseases "are systemic," potentially involving almost any organ in the body, it makes sense they could play a role in heart disease. She advised those affected to pay close attention to their health.

"Patients really need to be in touch with their physician so they can be screened and watch out for these other things (heart problems)," said Ghaw.

While both conditions' symptoms include painfully inflamed joints and possibly fever, lupus also causes skin rashes. Onset of lupus often occurs in late teens or early adulthood, but rheumatoid arthritis tends to start later, between the ages of 30 and 50, according to the Arthritis Foundation. A distinct but linked form of rheumatoid arthritis affects children.

Those with rheumatoid arthritis usually have a normal lifespan, but lupus can shorten people's lives because it often affects kidney function and other important organs, said Ghaw.

More information

To learn more about atrial fibrillation, visit the American Heart Association.