July 25, 2000 -- Here's some news Starbuck's probably doesn't want you to know: A new report suggests heavy coffee drinking may raise your risk of developing rheumatoid arthritis. The findings are based on two studies of more than 25,000 people in Finland.
"This is probably the most comprehensive look at a large number of patients to look at a potential risk factor," says Beth Jonas, MD. But Jonas, a clinical assistant professor of orthopaedic surgery at the University of North Carolina, Chapel Hill, and a board-certified rheumatologists, hastens to add that these findings raise many unanswered questions, and that the coffee-drinking habits of those in Finland may not be comparable to those of Americans. Jonas was not involved in the study.
Rheumatoid arthritis is inflammation of the lining of the joints in the body and can lead to deformity and disability. It occurs when the body's immune system attacks the joints, although it is not known why. There is also no cure.
Lead author M. Heliövaara, MD, and his colleagues at the Social Insurance Institution, Research and Development Centre in Turku, Finland, studied the association between coffee drinking, rheumatoid arthritis, and a blood marker called rheumatoid factor that is found in about half the cases of rheumatoid arthritis. They published their findings in the Annals of Rheumatic Disease.
In two large studies starting in the 1970s, Finnish adults were asked questions about their medical history and smoking and drinking habits, as well as their coffee intake. After following the adults for about 15 years, the researchers used health records to determine the number of people who went on to develop rheumatoid factor or rheumatoid arthritis.
Both studies showed an association between the number of cups of coffee drunk daily and the risk of producing rheumatoid factor. In fact, one of the studies showed those who drank four or more cups of coffee each day were twice is likely to have the marker for rheumatoid arthritis. They found the same results even when they adjusted for other risk factors such as age, obesity, alcohol consumption, and smoking.
The authors concluded that drinking coffee plays some role in the development of rheumatoid arthritis. They suggest that some ingredient in coffee triggers the production of rheumatoid factor, which may later lead to the disease.
But the authors also point out that, since the 1970s, approximately 75% of Finnish coffee drinkers have switched from drinking boiled coffee to drinking filtered coffee, and they suggest that the type of coffee consumed might have something to do with the relationship between coffee and rheumatoid arthritis.
Jonas agrees that the type of coffee needs to be considered. She notes that the authors apparently did not ask about the consumption of decaffeinated coffee. Also, Europeans in general like their coffee much stronger than Americans do. Both of these points make the data difficult to generalize to people in other countries.
"There are a number of unanswered questions here," Jonas tells WebMD. For example, although the investigators found an association between coffee and rheumatoid arthritis even in people who never smoked, Jonas points out that they did not ask about exposure to environmental or second-hand smoke.
The authors also failed to account for one of the most important early symptoms of rheumatoid arthritis: fatigue, says rheumatologist Cody Wasner, MD. Fatigue may precede the development of rheumatoid factor and other rheumatoid arthritis symptoms by a year or more, "and one of the ways in which people try to get more energy is to drink more coffee." Wasner, who practices in Eugene, Ore., is a spokesman for the Arthritis Foundation. Indeed, he tells WebMD, other factors associated with an increased risk of rheumatoid arthritis, such as smoking and being overweight, might also be reactions to the stress of feeling tired, which could be an early sign of the disease.
Jonas adds that rheumatoid factor is a marker, not a cause, of rheumatoid arthritis. "Fifty percent of patients with newly diagnosed rheumatoid arthritis are rheumatoid factor negative," she says.
"This research adds to our understanding of a disease," Jonas says. But neither she nor Wasner is advising their patients to boycott Starbucks yet. "[These results] don't mean that if you quit drinking coffee, you won't get rheumatoid arthritis," Wasner says. "That's clearly not the case."