Drinking three or more cups of decaffeinated coffee a day can double the risk of developing rheumatoid arthritis (RA) in women, compared to those who drink regular or no coffee, according to scientists at the University of Alabama in Birmingham, USA.

The conclusion, published in the US journal Arthritis and Rheumatism, was discovered after an 11-year study, conducted between 1986 and 1992. Researchers studied the dietary habits of 31,336 women across the US, aged 55 to 69, who exhibited no prior history of RA.
 
The study's lead author, rheumatologist Dr. Ted Mikuls, commented: "Decaffeinated coffee intake is significantly and positively associated with RA onset, especially among elderly women, while tea intake shows an inverse association.

"It is not known whether the presence or absence of caffeine per se explains the increased risk observed with coffee consumption, as opposed to a by-product related to the preparation and/or processing of the coffee products."