No Bones About It: Drinking Coffee May Increase Arthritis Risk
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."