Education As of 2020, about 17.6 million people around the world were living with rheumatoid arthritis — an autoimmune disease where the body’s immune system mistakenly attacks tissues lining the joints of the hands and feet, causing painful inflammation and swelling. Researchers are still unclear as to the exact cause of rheumatoid arthritis. However, previous studies show that genetics , environmental factors , smoking , and obesity may increase a person’s risk of developing the disease. “