<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by rheumatoid arthritis ? [/INST] Rheumatoid arthritis affects about 1.3 million adults in the United States. Worldwide, it is estimated to occur in up to 1 percent of the population. The disease is two to three times more common in women than in men, which may be related to hormonal factors. </s>