Mayo Clinic epidemiologists have found that the systemic inflammation characterizing rheumatoid arthritis may be to blame for the increased risk of cardiovascular death in patients with the disease.
"We believe that inflammation is a strong risk factor for cardiovascular disease among rheumatoid arthritis patients," says Hilal Maradit Kremers, M.D., lead study investigator and research associate in the Mayo Clinic Department of Health Sciences Research.
Rheumatoid arthritis patients have a significantly increased risk of dying of a heart condition if they have swelling in the large joints, rheumatoid vasculitis (inflammation of the blood vessels), rheumatoid lung disease or a high erythrocyte sedimentation rate (a blood test commonly known as ESR that measures level of inflammation in the body), report the investigators in the March issue of Arthritis & Rheumatism.
"Our previous research showed that rheumatoid arthritis patients have a higher risk of early death than others and that these deaths are mostly due to cardiovascular disease," says Sherine Gabriel, M.D., the study's senior author and Mayo Clinic rheumatologist, epidemiologist and chair of the Department of Health Sciences Research. "We suspect that systemic inflammation promotes this risk. Our findings support this hypothesis."
The exact means by which the inflammation in rheumatoid arthritis can lead to heart disease is unclear, say the Mayo Clinic investigators, who indicate this is currently under study. The investigators hypothesize that if the degree of a rheumatoid arthritis patient's inflammation can be closely monitored and kept under strict control, the risk of death by heart condition may decrease. This hypothesis is also the subject of ongoing research.
The study was conducted using the resources of the Rochester Epidemiology Project. The Mayo Clinic researchers followed a group of 603 Rochester residents diagnosed with rheumatoid arthritis between Jan. 1, 1955 and Jan. 1, 1995. The researchers collected detailed information about all study subjects' cardiac events and their cardiovascular risk factors, such as diabetes, blood pressure, cholesterol, body mass index and smoking. They also collected information on indicators of systemic inflammation and rheumatoid arthritis disease severity, such as rheumatoid factor positivity, ESR, joint swelling, radiographic changes, rheumatoid arthritis nodules, rheumatoid arthritis complications, rheumatoid arthritis treatments and disease duration. In addition, the researchers collected information on comorbitities, the presence of additional diseases. All patients were followed until death, migration from Rochester or Jan. 1, 2001.